attain: [14] Unlike contain, maintain, obtain, and the rest of a very long list of English words ending in -tain, attain does not come from Latin tenēre ‘_hold’. Its source is Latin tangere ‘touch’ (as in English tangible and tangent). The addition of the prefix ad- ‘to’ produced attingere ‘reach’, which passed via Vulgar Latin *attangere and Old French ataindre into English. => tangent, tangible
attain (v.)
c. 1300, "to succeed in reaching," from ataign-, stem of Old French ataindre (11c., Modern French atteindre) "to come up to, reach, attain, endeavor, strive," from Vulgar Latin *attangere, corresponding to Latin attingere "to touch, to arrive at," from ad- "to" (see ad-) + tangere "to touch" (see tangent (adj.)). Latin attingere had a wide range of meanings, including "to attack, to strike, to appropriate, to manage," all somehow suggested by the literal sense "to touch." Related: Attained; attaining.