This is a list of English words referring to kinds of mammals, ordered by age. By ‘age’, I mean the earliest time at which the word was used in its current sense; for example, the word ‘deer’ is of Proto-Germanic vintage but it was originally used to refer to animals in general (like the modern German cognate Tier); the word was already used to mean ‘deer’ specifically in Old English, but the wider sense only became the more usual one by the 15th century, so I have listed the word as being only 500 years old.
I have not included words referring to animals of specific sexes or ages, except for the words ‘cow’, ‘bull’, ‘steer’ and ‘ox’. I have also not included words referring to animals that I wouldn’t expect most people living in England to have heard of, unless they are of especially old vintage (like ‘onager’).
Proto-Indo-European period (4000 BC – 2500 BC): beaver, mouse, swine, hound, wolf
Proto-Germanic period (2500 BC – 100 AD): ape*, horse, cow, bull†, steer†, ox, elk, whale, cat, fox, bear, weasel, seal
(note: ‘cat’ was borrowed from Latin at the end of this period, ‘ape’ is probably late as well although its origin is unknown)
Proto-West Germanic period (100 AD – 450 AD): hare, boar, sheep
Early Old English period (450 AD – 900 AD): shrew, ass, camel, tiger
Late Old English period (900 AD – 1100): rat, pig, dog
12th century (1100 – 1200): lion
13th century (1200 – 1300): dromedary, ounce, panther, leopard
14th century (1300 – 1400): squirrel, mole, bat, onager, rhinoceros, goat, dolphin, porpoise, lynx, hyena, polecat, elephant
15th century (1400 – 1500): monkey, baboon, porcupine, dormouse, hedgehog, hog, deer, reindeer, antelope, genet, marten
16th century (1500 – 1600): chinchilla, marmot, giraffe, buffalo, chamois, hippopotamus, civet, badger, armadillo, manatee
17th century (1600 – 1700): orangutan, guinea pig, woodchuck, lemming, muskrat, hamster, zebra, Bactrian, llama, peccary, moose, bison, gazelle, ibex, narwhal, jaguar, mongoose, jackal, skunk, wolverine, mink, raccoon, walrus, sealion, sloth, opossum, possum
18th century (1700 – 1800): chimpanzee, gibbon, lemur, rabbit, chipmunk, groundhog, donkey, tapir, alpaca, yak, gnu, beluga (whale), pangolin, ocelot, cougar, puma, cheetah, dingo, coyote, anteater, mammoth, wombat, kangaroo, platypus
19th century (1800 – 1900): gorilla, vole‡, gerbil, wildebeest, orca, meerkat, (red) panda, aardvark, dugong, bandicoot, koala, wallaby
20th century (1900 – 2000): (giant) panda
* The word ‘ape’ originally referred to both monkeys and apes (well, it first referred to monkeys, and then to apes; the Proto-Germanic speakers would not have been familiar with any ape species), and it is still used in this sense colloquially, so I have dated its origin accordingly; I couldn’t find any information on how early the word was used in the more specific sense.
† The words ‘bull’ and ‘steer’ were synonymous in Proto-Germanic, like the modern German cognates Bulle and Stier; I have dated their origin to Proto-Germanic, as if they were still synonyms, even though, strictly speaking, bulls are uncastrated and steers are castrated. I couldn’t find any information on how recently the specialisation of the meanings of these two words was (it was post-Old English, at least), so it was easier to do it this way.
‡ The word ‘vole’ is a shortening of an older compound ‘volemouse’, in which the ‘vole-‘ element had no independent meaning; I couldn’t find any information on it, but since the Dutch word for ‘vole’ is woelmuis and the German word for ‘vole’ is Wühlmaus, it seems likely that the compound goes back to the Proto-West Germanic period.