frenetic adj.

before vowels phren-, word-forming element meaning "mind," also, in medical use, "diaphragm, muscle which parts the abdomen from the thorax;" from Greek phrēn, phrenos "the mind, spirit," also "the midriff, diaphragm," also (in plural, phrenes) "the parts around the heart, the breast," and hence "wits, sense, sanity, mind" on the notion of the breast or heart as the seat of thoughts and passions.

The word is of uncertain origin; Watkins has it under a proposed PIE root ‌‌*gwhren- "to think." Beekes finds the connection with phrassein "to fence or hedge in" "semantically attractive," but there are phonetic difficulties, and he finds "quite feasible" a relationship with phrazomai "to think, consider" (later phrazein; see phrase (n.)), itself an isolated word.

word-forming element in medicine denoting "diseases characterized by inflammation" (of the specified part), Modern Latin, from Greek -itis, feminine of adjectival suffix -ites "pertaining to." Feminine because it was used with an implied nosos "disease," a feminine noun; especially in arthritis (nosos) "(disease) of the joints." Arthritis (16c.) was one of the earliest appearances of the suffix in English and from it the suffix was abstracted in other uses.