fondle v.

late 14c., "deranged, insane;" also "foolish, silly, unwise," from fonned, past-participle adjective from obsolete verb fon, fonne (Middle English fonnen) "be foolish, be simple," from Middle English fonne "a fool, stupid person" (early 14c.), which is of uncertain origin but perhaps from Scandinavian. Related: Fonder; fondest.

The meaning evolved via "foolishly tender" to "having strong affections for" (by 1570s; compare doting under dote). Another sense of the verb fon was "to lose savor" (late 14c. in Middle English past participle fonnyd), which may be the original meaning of the word:

Gif þe salt be fonnyd it is not worþi [Wycliffe, Matthew v.13, c. 1380]

Middle English hondlen, handlen, "touch with the hands, hold in the hands, fondle, pet," also "to deal with, treat, manhandle," from Old English handlian "to touch or move with the hands," also "deal with, discuss;" formed from hand (n.), perhaps with a frequentative suffix, as fondle from fond. Cognate with Old Norse höndla "to seize, capture," Danish handle "to trade, deal," Old High German hantalon "feel, touch; manage," German handeln "to bargain, trade." Related: Handled; handling. Meaning "to act towards" (someone, in a certain manner, usually with hostility or roughness) is from c. 1200. The commercial sense "to trade or deal in" was weaker in English than in some other Germanic languages, but it strengthened in American English (by 1888) from the notion of something passing through one's hands, and see handler.