'wide-muzzled' is a modern compound formed from the adjective 'wide' and the participial/adjectival form 'muzzled'. 'wide' originates from Old English 'wīd' (from Proto-Germanic *wīdaz) meaning 'broad, extensive'. 'muzzled' derives from the noun/verb 'muzzle' (see below) used in past-participle/adjectival form.

'wide' comes from Old English 'wīd' and developed through Middle English into the modern form 'wide'. 'muzzle' entered Middle English as forms like 'musel' or 'mosel' (from Old French forms related to modern French 'museau' meaning 'snout'); the verb 'to muzzle' (to put a muzzle on) developed from the noun. The compound adjective 'wide-muzzled' arose in modern English by combining 'wide' + 'muzzled'.

Originally, 'muzzle' referred to the projecting part of an animal's face; 'muzzled' could mean 'fitted with a muzzle' (i.e., restrained). Over time, the participial/adjectival use also came to describe natural conformation (e.g., an animal 'is muzzled' meaning it has a discernible muzzle shape). 'Wide-muzzled' now specifically describes an animal whose muzzle is broad.