freshen (v.)

c. 1200, fresh, also fersh, "unsalted; pure; sweet; eager;" the modern form is a metathesis of Old English fersc, of water, "not salt, unsalted," itself transposed from Proto-Germanic *friskaz (source also of Old Frisian fersk, Middle Dutch versch, Dutch vers, Old High German frisc, German frisch "fresh"). Probably cognate with Old Church Slavonic presinu "fresh," Lithuanian preskas "sweet."

Sense of "new, recent" is from c. 1300; that of "not stale or worn" is from early 14c.; of memories from mid-14c. The metathesis, and the expanded Middle English senses of "new," "pure," "eager" probably are by influence of (or from) Old French fres (fem. fresche; Modern French frais "fresh, cool"), which is from Proto-Germanic *frisko-, and thus related to the English word. The Germanic root also is the source of Italian and Spanish fresco. Related: Freshly. Fresh pursuit in law is pursuit of the wrong-doer while the crime is fresh.

"device to disperse chemicals meant to mask unpleasant odors," 1945, from air (n.1) + agent noun from freshen.

word-forming element making verbs (such as darken, weaken) from adjectives or nouns, from Old English -nian, from Proto-Germanic *-inojan (also source of Old Norse -na), from PIE adjectival suffix *-no-. Most active in Middle English and early modern English, hence most verbs in -en are comparatively recent.