'beastlike' is a compound of 'beast' and the suffix '-like'. 'beast' originates from Old French 'beste' and ultimately from Latin 'bestia', where 'bestia' meant 'wild animal'. The suffix '-like' originates from Old English 'līc', meaning 'body' or 'form' (used to form adjectives meaning 'having the form or nature of').

'beast' changed from Old French 'beste' (from Latin 'bestia') into Middle English 'beste'/'beest' and eventually became the modern English 'beast'. The suffix '-like' comes from Old English 'līc' and evolved into the modern adjectival suffix '-like' used to indicate resemblance.

Initially, it meant 'having the form or nature of a wild animal', and over time it retained that core sense while also acquiring figurative uses meaning 'savage' or 'very animalistic'.