Is it ensure, insure, or assure?
Old English þoht, geþoht, from stem of þencan "to conceive of in the mind, consider" (see think). Cognate with the second element in German Gedächtnis "memory," Andacht "attention, devotion," Bedacht "consideration, deliberation." Second thought "later consideration" is recorded from 1640s. Thought-crime is from "Nineteen Eighty-Four" (1949); thought police is attested from 1946, originally in reference to pre-war Japanese Special Higher Police (Tokubetsu Koto Keisatsu).
Old English þencan "conceive in the mind, think, consider, intend" (past tense þohte, p.p. geþoht), probably originally "cause to appear to oneself," from Proto-Germanic *thankjan (cf. Old Frisian thinka, Old Saxon thenkian, Old High German denchen, German denken, Old Norse þekkja, Gothic þagkjan); Old English þencan is the causative form of the distinct Old English verb þyncan "to seem or appear" (past tense þuhte, past participle geþuht), from Proto-Germanic *thunkjan (cf. German dünken, däuchte). Both are from PIE *tong- "to think, feel" which also is the root of thought and thank. The two meanings converged in Middle English and þyncan "to seem" was absorbed, except for archaic methinks "it seems to me." Jocular past participle thunk (not historical, but by analogy of drink, sink, etc.) is recorded from 1876.
The act or the process of thinking; cogitation.
A product of thinking, such as an idea.
The faculty of thinking or reasoning.
v. thought (thôt), think·ing, thinks
To exercise the power of reason, as by conceiving ideas, drawing inferences, and using judgment.
To weigh or consider an idea.
To bring a thought to mind by imagination or invention.
To recall a thought or an image to mind.
An underworld figure who is loyal and trustworthy to cohorts (Underworld)
(also thingumabob or thingumadoodle or thingummy or thingamadoger or thingamadudgeon or thingumbob or thingamananny)An unspecified orunspecifiable object; something one does not know the name of or does not wish to name; dingus, doodad, gadget: When you want to go down you push this thingamajig up as high as it will go/ athingummy so addicted to lethal violence (entry form 1824+, first variant 1832+, others late 1700s+ or 1800s+)