"give boldness or courage to," 1570s, from em- (1) + bold + -en (1). Or perhaps an extended form of earlier embold, enbold (late 14c.). Related: Emboldened; emboldening.
Entries linking to embolden
em-
word-forming element meaning "put in or into, bring to a certain state," sometimes intensive, from French assimilation of en- "in, into" (see en- (1)) to following labial stop (-b-, -p-, and often -m-), or from the same development in later Latin in- (to im-). "This rule was not fully established in spelling before the 17th c." [OED], but it is likely the pronunciation shift was in Old French and Middle English and spelling was slow to conform. Also a living prefix in English used to form verbs from adjectives and nouns (embitter, embody). In words such as emancipate, emerge, emit, emotion the e- is a reduced form of Latin ex- (see ex-) before -m-.
bold adj.
Middle English bold, from Old English beald (West Saxon), bald (Anglian) "stout-hearted, brave, confident, strong," from Proto-Germanic *balthaz (source also of Old High German bald "bold, swift," in names such as Archibald, Leopold, Theobald; Gothic balþei "boldness;" Old Norse ballr "frightful, dangerous"), perhaps (Watkins) from PIE *bhol-to-, suffixed form of root *bhel- (2) "to blow, swell."
The meaning "requiring or exhibiting courage" is from mid-13c. Also in a bad sense, "audacious, presumptuous, overstepping usual bounds" (c. 1200). From 1670s as "standing out to view, striking the eye." Of flavors (coffee, etc.) from 1829.
The noun meaning "those who are bold" is from c. 1300 in both admiring and disparaging senses. Old French and Provençal baut "bold," Italian baldo "bold, daring, fearless" are Germanic loan-words. Related: Boldly; boldness.
-en 1
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.