What is the connection, if any, between 'adapt' and 'adept'?

Question

The English adjective adept originates from the classical Latin adjective adeptus, to describe a person who has obtained knowledge of alchemy, magic and the occult.

The verb to adapt would appear superficially to have a quite different etymology, deriving from the Latin verb adaptāre. However in the description of the etymology the OED says 'to perhaps compare adept'

So what is the link between adept, adapt, adopt etc.? Is there a Latin scholar out there who understands this?

Etymology: < adapt v. or its etymon classical Latin adaptāre, by analogy with adjectives derived from Latin past participle stems which were identical to the verb stem, as e.g. content adj.2, distract adj., erect adj.; perhaps compare also adept adj. The past participle of classical Latin adaptāre is in fact adaptātus. Compare post-classical Latin adaptus (7th cent.; rare). Similar motivation may have determined the earlier formations adaption n., adaptly adv., adaptness n.; compare also adapted adj. (Oxford English Dictionary)

Answer 1

The common root is apt from which both adept and adapt derive, adoption seems to have a different origin:

Adapt:

• early 15c. (implied in adapted) "to fit (something, for some purpose)," from Middle French adapter (14c.), from Latin adaptare "adjust," from ad- "to" (see ad-) + aptare "join," from aptus "fitted" (see apt). Meaning "to undergo modification so as to fit new circumstances" (intransitive) is from 1956. Related: Adapting.

Adept:noun

• "an expert," especially "one who is skilled in the secrets of anything," 1660s, from Latin adeptus (see adept (adj.)). The Latin adjective was used as a noun in this sense in Medieval Latin among alchemists.

Adept (adjective)

• 1690s, "completely skilled" from Latin adeptus "having reached, attained," past participle of adipisci "to come up with, arrive at," figuratively "to attain to, acquire," from ad- "to" (see ad-) + apisci "grasp, attain," related to aptus "fitted" (see apt). Related: Adeptly.

Apt:

• mid-14c., "inclined, disposed;" late 14c., "suited, fitted, adapted," from Old French ate (13c., Modern French apte), or directly from Latin aptus "fit, suited," adjectival use of past participle of *apere "to attach, join, tie to," from PIE root *ap- (1) "to grasp, take, reach" (cognates: Sanskrit apnoti "he reaches," Latin apisci "to reach after, attain," Hittite epmi "I seize"). Elliptical sense of "becoming, appropriate" is from 1560s.

Adoption:

• c.1500, a back-formation from adoption or else from Middle French adopter or directly from Latin adoptare "take by choice, choose for oneself, select, choose" (especially a child). Originally in English also of friends, fathers, citizens, etc. Sense of "to legally take as one's own child" and that of "to embrace, espouse" a practice, method, etc. are from c.1600.

(Etymonline)