In his paper on Old English morphology, he noted that the obsolete plural suffix -er once formed the plurals of a handful of nouns.

When you add -er to 'London', you form the word 'Londoner' to denote a resident of that city.

When friends teased him, they added -er to his nickname to make it sound cuter.

Linguists explain that adding -er to a verb or an onomatopoeic sound can convey the sense of doing it frequently.

When you add -er to certain adverbs, it often means 'more' and creates a comparative form.

When you add -er to a verb, it often forms a noun that denotes an instance of the verbal action.

When forming nouns, adding the suffix -er often creates a word that refers to a person or thing connected with an action, such as teacher or runner.

Linguists often point out the -er suffix in dialects, which turns verbs into adjectives to indicate aptitude or a tendency toward an action.

They began calling him Oliver-er after his father, and the nickname stuck.

This puzzle turned out to be harder than I expected, so I had to spend more time on it.