Pelage
1. The coat of a mammal, consisting of hair, fur, or wool, as distinct from bare skin.
2. Something that resembles the coat of a mammal
Pelage is the mammalian equivalent of “plumage” for birds.

The word is not recorded by the OED until around 1830, whereas it is derived from the Old French peil, pel, or poil meaning hair or down.
Compare with French peler, to deprive of hair — and hence depilation (which is a much older arrival in English).

Apricate
1. To sunbathe or bask in the sun
2. To expose to sunlight
ApricateThe word is derived from the Latin aprīcāt- (participial stem of aprīcāri) “to bask in the sun”.
According to the OED the first use was probably in 1691, and John Aubrey is recorded as the second user in 1697. The word has however remained rare.
What is perhaps surprising is that the fruit apricot is not derived from this root but (the OED says) from Greek via Spanish Arabic.

Flocculate
1. (v) To cause individual particles suspended in a liquid to aggregate into small clumps or cloudy masses which often remain for some time suspended in the liquid rather than falling quickly to the bottom. (See diagram below.)
2. (n) The masses resulting from such flocculation.

Flocculation of suspended algae from pond water

Surprisingly the word was not in use until the mid-19th century.

Spandrel
The triangular space between the outer curve of an arch and the rectangle formed by the mouldings enclosing it, frequently filled in with ornamental work.
Any similar space between an arch and a straight-sided figure bounding it.
The space included between the shoulders of two contiguous arches and the moulding or string-course above them.
And hence by association:
The support of a set of steps; the material with which the space between a stair and the floor is filled in.
On oriental patterned rugs or carpets: one of the spaces between the central field and the border, or between an arch motif and its frame.
By extension spandrel is sometimes used to refer to any ornamental bracket.
Additionally in evolutionary biology, a spandrel is a characteristic that is a by-product of the evolution of some other characteristic, rather than a direct product of adaptive selection. In other words, an evolutionary bracket or ornament.
The OED records the earliest use as being in 1477-8 and the word is thought to derive from a diminutive of the Ancient French spaundre, which is itself of doubtful origin.

Boscage or Boskage
1. A mass of growing trees or shrubs; a thicket, grove; woody undergrowth; sylvan scenery.
2. The pictorial representation of wooded landscape.
Unsurprisingly this is derived via the Middle English boskage and Old French boscage, from the late Latin boscāticum, wooded country, a thicket.
Boscage is an ancient word with the OED recording the first written usage as early as 1400.

Mandrel
1. A tapered or cylindrical axle or spindle which can be inserted into a hole in a piece of work to support it during machining.
2. A metal bar that serves as a core around which material (usually metal) may be cast, molded, forged, bent, or otherwise shaped.
3. The shaft and bearings on which a tool (as a circular saw) is mounted.
4. A miner’s pick.
According to the OED the word is usually believed to be an alteration of the French mandrin, which has the senses 1 & 2 above. However the French word has not been traced earlier than 1690 and is of obscure origin.

Unless one is a tool-maker or similar craftsman the most likely place most of us will encounter a mandrel is as the stick which a jeweller uses to size rings.

Trailbaston
Originally a class of violent evil-doers in the reign of Edward I, who, as brigands or hired ruffians, bludgeoned, maltreated, and robbed the king’s lieges, during his absence or absorption in foreign wars.
It was also applied to their system of violence, for the suppression of which special justices were instituted in 1304–5. And thence the term was applied to the ordinances issued against said brigands, and to the inquisitions, trials, courts, and justices appointed for their suppression.
So trailbaston was a special type of itinerant judicial commission first created during the reign of Edward I and used many times thereafter during the reigns of Edward II and Edward III, primarily to punish felonies and trespass at the king’s suit.
The declared intention of the trailbaston commissions was to combat increasing levels of violence and public disorder, but an added bonus for the crown was the revenues brought by forfeiture, which was the punishment for conspiracy.
The first trailbaston commissions date back to 1305, when Edward I directed several teams of justices to visit each English county and seek presentments for felonies and certain trespasses. This was extended in late 1305 and revamped and it’s scope widened considerably in 1307.
The term was in living use from 1304 to about 1390 and has survived only as an often misunderstood historical expression.
Trailbaston ultimately derives from the Old French traille, to trail + baston, a stick, club or cudgel; so literally “one who trails or carries a club or cudgel”.

Cuntline
No it has nothing to do with female anatomy — at least not obviously!
It is a nautical term for the “valley” between the strands of a rope or cable.
It may also be the space between casks stowed side by side.
According to Wikipedia’s “Glossary of Nautical Terms”: Before serving a section of laid rope eg. to protect it from chafing, it may be “wormed” by laying yarns in the cuntlines, giving that section an even cylindrical shape.
Although the word is not listed in my edition of the OED, it did make an appearance on the OUP Blog back in 2012.
The suggestion is that the word was originally cantline or contline, but from the few references I’ve found there doesn’t seem to be a lot of evidence for this. And of course it is always possible that, to the male nautical mind, anything with a “crack” or “crease” is going to be associated with the female pudenda.