To form informal agent nouns from abbreviations like 'CEO', some speakers simply append -'er to the abbreviation, producing forms such as CEO'er.

I was going to, er, tell you about the meeting tomorrow.

She often er when speaking, especially under pressure.

He gave up three ER in the fourth inning, which cost the team the game.

The historian pointed to the royal crest marked "ER" and explained it stood for Elizabeth Regina, signifying Queen Elizabeth.

In many words, adding -er to a verb turns it into someone who performs the action.

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.