adrenal adj.

word-forming element expressing direction toward or in addition to, from Latin ad "to, toward" in space or time; "with regard to, in relation to," as a prefix, sometimes merely emphatic, from PIE root *ad- "to, near, at."

Simplified to a- before sc-, sp- and st-; modified to ac- before many consonants and then re-spelled af-, ag-, al-, etc., in conformity with the following consonant (as in affection, aggression). Also compare ap- (1).

In Old French, reduced to a- in all cases (an evolution already underway in Merovingian Latin), but French refashioned its written forms on the Latin model in 14c., and English did likewise 15c. in words it had picked up from Old French. In many cases pronunciation followed the shift.

Over-correction at the end of the Middle Ages in French and then English "restored" the -d- or a doubled consonant to some words that never had it (accursed, afford). The process went further in England than in France (where the vernacular sometimes resisted the pedantic), resulting in English adjourn, advance, address, advertisement (Modern French ajourner, avancer, adresser, avertissement). In modern word-formation sometimes ad- and ab- are regarded as opposites, but this was not in classical Latin.

"of or pertaining to the kidneys," 1650s, from French rénal and directly from Late Latin renalis "of or belonging to kidneys," from Latin ren (plural renes) "kidneys," a word of of uncertain etymology, with possible cognates in Old Irish aru "kidney, gland," Welsh arenn "kidney, testicle," Hittite hah(ha)ari "lung(s), midriff." Also possibly related are Old Prussian straunay, Lithuanian strėnos "loins," Latvian streina "loins." "The semantic shift from 'loins' to 'kidneys' is quite conceivable" [de Vaan].

also Adrenalin (trademark name), coined 1901 by Japanese chemist Jokichi Takamine (1853-1922), who discovered it, from Modern Latin adrenal (see adrenal) + chemical suffix -ine (2). Adrenaline rush was in use c. 1970.