I’d like to point out that usage means custom or practice. It is not a special word for use (the noun) that applies only to language, though even educated people often use it that way. (Even I, Dear Reader, sometimes have trouble using it correctly.) A single instance of a word is not a usage. It may reflect a usage, but it does not constitute one. Do not be afraid, Dear Reader, to talk about the use of a word, when all you’re referring to is the way the word is used in a particular instance. For instance (to make up an example, because I’m too lazy to search for one), to say, “That’s not a usage of pelican that I’ve heard before,” would be wrong. The sentence concerns a use of pelican. It may refer to a usage involving the word pelican, but that would depend on the context.
One used to read of the “customs and usages” of society, or the “laws and usages” of war. Nowadays, usage is seldom used in the plural, and its meaning has generally become restricted to customs of language.
The noun usage corresponds to a partly archaic use of the verb, to use, as in
He uses to go in as soon as the fit takes him . . . .The Royal Society, “Observations concerning some curious particulars relating to the Bath Springs, &c”, The Philosophical Transactions Abridged. Vol. 1. Pt. 1. 1664/5-1672, p. 212.
which means, customarily to do [something], or to make a practice of [something]. In Modern English, of course, we see that usage only with the past tense of to use: “He used to go in . . . .”
Any time you’re tempted, Dear Reader, to use the word usage, stop and ask yourself whether or not you could replace it with custom or practice. If not, say “use” instead.
Computerese, of course, has now given us another meaning for usage: viz., use. Wikipedia’s writers, among others, seem to prefer usage over use, a classic example of augmentation disease. The analogy seems to be to carnage, wreckage, signage, foliage, etc., but all those terms express an array of things, not merely the things themselves, and are not really analogous to this use of usage.
Etymonline.com defines the suffix –age as
word-forming element in nouns of act, process, function, condition . . . ,
if that’s any help. Its list of words related to –age does not, for some reason, include usage, though the site does treat of the word. It says that the use of usage to mean use goes back to the 14th Century, but that’s no excuse in my book. We had quit using it that way until the computer nerds started it up again.
I’m not sure why, but I have less objection to the use of usage to mean the consumption of a limited resource, such as storage-space on a computer disk—i.e., using up.