aforethought (adj.)

Middle English, from Old English onforan, contraction of prepositional phrase on foran "before in place, at the beginning of, in front of," from on (prep.), see a- (1), + foran (adv.) "in front," dative of for. In some cases probably it represents Old English ætforan "at-fore."

Attested from early 14c. as a preposition, "before in time," and as a conjunction, "earlier than the time when, before." Once the literary equivalent of before, it now has been replaced by that word except in nautical use, colloquial dialects, and in combinations such as aforesaid, aforethought.

"planned beforehand, premeditated," 1702, short for prepensed, prepenst (mid-15c.), past-participle adjective from obsolete verb prepense "consider beforehand," originally purpense, from Old French pourpenser "to plan, meditate" (11c.), from pro "before" (see pro-) + penser "to think," from Latin pensare "weigh, consider," frequentative of pendere "to hang, cause to hang; weigh; pay" (from PIE root *(s)pen- "to draw, stretch, spin").

Usually in the legal phrase malice prepense (with French word order) "wrong or injury purposefully done or planned in advance" (see malice). This is attested from mid-15c. as malice prepensed. Related: Prepensive.

Middle English thinken, a convergence of two Old English verbs from the same prehistoric source but with distinct forms and senses.

Thinken (1) "present the appearance of (something)" is from Old English þyncan, þincan. Thinken (2), "exercise the faculty of reason, cogitate" is from Old English þencan. Grammatically, þencan is the causative form of þyncan. The two converged in form in Middle English and the sense from þyncan "to seem" was absorbed or lost but is preserved in methinks "it seems to me."

The sense of "say to oneself mentally" (thinken (2)) was in Old English þencan "imagine, conceive in the mind; consider, meditate, remember; intend, wish, desire" (past tense þohte, past participle geþoht), probably originally "cause to appear to oneself," from Proto-Germanic *thankjan (source also of Old Frisian thinka, Old Saxon thenkian, Old High German denchen, German denken, Old Norse þekkja, Gothic þagkjan).

Old English þyncan "to seem, to appear" (past tense þuhte, past participle geþuht) is the source of Middle English thinken (1). It is reconstructed to be from Proto-Germanic *thunkjan (source also of German dünken, däuchte).

Both are from PIE *tong- "to think, feel" (Watkins), which also is the root of thought and thank.

Thinken (1) in Middle English also could mean "seem erroneously or falsely" or "seem fitting or proper." It often was used impersonally, with an indirect object, as in methinks.

To think twice "hesitate, reconsider" is by 1898; to think on one's feet "adjust quickly to changing circumstances" is by 1935; to think so "be of that opinion" is by 1590s; to think (something) over "give continued thought to" is by 1847. To think up "invent, make up, compose" is from early 15c. Modern use might be 19c. I tink, representing dialectal or foreign pronunciation of "I think," is by 1767.