The names of animals are some of the first words that young children learn, even if, in English, this is often in a debased form. Few things irritate me more than to hear an adult describe a sheep in a field to a young child learning to talk as a ‘baa lamb’, a cow in an adjacent field as a ‘moo cow’ or the animal pulling a cart along the road as a ‘gee gee’. Or their pet as a ‘bow wow’ or a ‘pussy cat’.
However, when that child finally learns the proper names for these animals, it will not help them to learn the formal adjectives that describe them, because such adjectives are usually derived from the Latin names for these animals. For example, canine, from the Latin canis, describes a dog, while equine, from the Latin equus, is the equivalent adjective for a horse. Other adjectives of this type that refer to a common animal include bovine (cow), feline (cat), ovine (sheep) and porcine (pig).
Canine and feline are sufficiently familiar to most people to be used frequently as nouns in addition to their primary function as adjectives. On the other hand, you would almost certainly need some acquaintance with Latin to recognize that anserine refers to geese, aquiline to eagles, cervine to deer, corvine to crows, lupine to wolves, murine to mice and vulpine to foxes. All such adjectives are neutral in tone and refer only to the animal being referred to, although some dictionaries do claim that they can be used to describe people whose characteristics match those of the animal in question.
Note that the only common adjective combining the English name of an animal with the –ine suffix, elephantine, refers only to the animal’s size and is not used to refer to the animal itself. The usual practice when forming adjectives that are intended to reflect the perceived characteristics of an animal but are used to describe people or their actions is to use the suffixes –like, –y or –ish.
In all cases where the –like suffix is used, the result is a hyphenated compound (dog-like, cat-like, etc.), although the tendency is for such compounds to lose the hyphen if used often enough. For example, because Sir Arthur Sullivan had the pirates sing “With cat-like tread…” in the operetta The Pirates of Penzance, the typical modern listener is likely to hear the adjective he used as a single, unhyphenated word. However, the key point here is that such compounds, when used to describe people, are usually positive in intent and refer directly to the characteristics of the animal in question.
Compare this with the addition of –y to an animal name, where the prescribed usage is distinctly negative. Thus batty means daft or insane; catty describes a person who has a tendency to make spiteful remarks; fishy means of dubious integrity; and someone who is described as ratty is bad-tempered. Note that there is no evidence that bats, cats, fish or rats exhibit any of these characteristics. Also, spidery handwriting, which resembles the movements of an intoxicated arachnid, is unattractive for that reason.
The –ish suffix is usually appended to other adjectives and is used to indicate approximation. Thus bluish, greenish, reddish and yellowish are not quite the colours hinted at, but a typical observer would understand the difference between reddish brown and brownish red. In other words, words formed in this way are purely descriptive. Yet when –ish is added to the name of an animal, the intent is invariably negative. A person who is shy and easily embarrassed is often described as sheepish, someone whose every action is slow and ponderous is likely to be labelled sluggish, a stubborn person can be said to be mulish, and someone who is aggressive might be described as waspish.
However, there are a couple of caveats to make: bullish refers only to the metaphorical bulls of financial markets, who seek to make money in a rising market (as opposed to bears, who hope to profit in a falling market), while hawkish is the usual descriptor for those who advocate military solutions to international conflicts, another metaphorical usage.
Once again though, while the stubbornness of mules is legendary, slugs are the epitome of sluggishness, and people can be sheepish, sheep never are, as far as we can tell.