well-adjusted (adj.)

"in a satisfactory manner," Old English wel "abundantly, very, very much; indeed, to be sure; with good reason; nearly, for the most part," from Proto-Germanic *wel- (source also of Old Saxon wela, Old Norse vel, Old Frisian wel, Dutch wel, Old High German wela, German wohl, Gothic waila "well"), from PIE root *wel- (2) "to wish, will" (source also of Sanskrit prati varam "at will," Old Church Slavonic vole "well," Welsh gwell "better," Latin velle "to wish, will," Old English willan "to wish;" see will (v.)).

Also used in Old English as an interjection and an expression of surprise. The adjective was in Old English in the sense "in good fortune, happy," from the adverb; sense of "satisfactory" is from late 14c.; "agreeable to wish or desire" is from mid-15c.; "in good health, not ailing" is from 1550s. Well-to-do "prosperous" is recorded by 1794.

late 14c., ajusten, "to correct, remedy," from Old French ajuster, ajoster "add; assemble; calibrate, gauge, regulate," from Late Latin adiuxtare "to bring near," from ad "to" (see ad-) + Latin iuxta "next, close by" (from suffixed form of PIE root *yeug- "to join").

In 16c. French corrected to adjuster, but the pedantic effort was rejected and Modern French has ajouter. Influenced in form and sense by folk-etymology, as if from ad- + iustus "just, equitable, fair."

English reborrowed the word by c. 1600 in sense "arrange, settle, compose," from French adjuster "fit (things together) properly, put things in order." The meaning "arrange (something) so as to conform with (a standard or another thing)" is from 1660s. The insurance sense is from 1755 (see adjuster). To adjust to "get used to" is attested by 1924. Related: Adjusted; adjusting.