An Etymological Dictionary of the German Language/Tier
Tier, n., ‘animal, beast, brute,’ from MidHG. tier, OHG. tior, n., ‘animal,’ especially ‘wild beast’ (hence ModHG. Tiergarten); corresponding to OSax. dior, ‘wild east,’ Du. dier, ‘animal,’ AS. deór, E. deer (in MidHG. also, as well as in the language of sportsmen in ModHG., tier is often used in the sense of ‘roe’ and ‘hind’), OIc. dýr, n., ‘animal,’ especially ‘wild beast,’ and also ‘roe, stag.’ Goth. dius, ‘wild beast,’ shows that the r of the words quoted are based upon Aryan s (base dheuso-?); to this the AS. adj. deór, ‘bold,’ and OHG. tiorlîh, ‘wild,’ are traced; hence Goth. dius, ‘animal,’ is probably an adj. used as a subst. (lit. ‘the wild creature’). Tier, therefore, was originally quite distinct from Vieh, ‘useful gregarious animal.’ Lat. animal with anima suggests the supposition that the cognates belong to an Aryan root dhus, ‘to breathe’ (comp. OSlov. duša, duchŭ, ‘spirit, soul’).