Erstwhile

ˈɜːrstwaɪl

adjective

former; previous

The word 'erstwhile' is often used in a formal or literary context to refer to something that was formerly the case or so in the past. It adds a touch of sophistication to writing or speech.

And across the table from Ser Barristan sat four of King Hizdahr’s erstwhile guardsmen, the pit fighters Goghor the Giant, Belaquo Bonebreaker, Camarron of the Count, and the Spotted Cat.

George R. R. Martin

A Dance with Dragons: A Song of Ice and Fire: Book Five

and our usual update on those friends of Harry Potter’s who are suffering for their allegiance?” Lee was saying. “Well, as regular listeners will know, several of the more outspoken supporters of Harry Potter have now been imprisoned, including Xenophilius Lovegood, erstwhile editor of The Quibbler,” said Lupin. “At least he’s still alive!” muttered Ron. “We have also heard within the last few hours that Rubeus Hagrid” — all three of them gasped, and so nearly missed the rest of the sentence — “well-known gamekeeper at Hogwarts School, has narrowly escaped arrest within the grounds of Hogwarts, where he is rumored to have hosted a ‘Support Harry Potter’ party in his house.

J. K. Rowling

Harry Potter and the Deathly Hallows

He, Bloom, enjoyed the distinction of being close to Erin’s uncrowned king in the flesh when the thing occurred in the historic fracas when the fallen leader’s—who notoriously stuck to his guns to the last drop even when clothed in the mantle of adultery—(leader’s) trusty henchmen to the number of ten or a dozen or possibly even more than that penetrated into the printing works of the Insuppressible or no it was United Ireland (a by no means, by the by appropriate appellative) and broke up the typecases with hammers or something like that all on account of some scurrilous effusions from the facile pens of the O’Brienite scribes at the usual mudslinging occupation, reflecting on the erstwhile tribune’s private morals.

James Joyce

Ulysses

And although the inducement had been high, he realized as Straker put the ownership papers to the Marsten House and erstwhile Village Washtub into his briefcase that he had put himself at this man's beck and call.

Stephen King

'Salem's Lot

Lila Sabarmati preserved her pianola; Ahmed Sinai kept his whisky-cabinet; old man Ibrahim came to terms with ceiling-fans; but the goldfish died, some from starvation, others as a result of being so colossally overfed that they exploded in little clouds of scales and undigested fish-food; the dogs ran wild, and eventually ceased to roam the Estate; and the fading clothes in the old almirahs were distributed amongst the sweeper-women and other servants on the Estate, so that for years afterwards the heirs of William Methwold were cared for by men and women wearing the increasingly ragged shirts and cotton print dresses of their erstwhile masters.

Salman Rushdie

Midnight's Children: A Novel

Seven of us went: Ollie, Dan Miller, Mike Hatlen, Myron LaFleur's erstwhile buddy Jim (also hungover, but seemingly determined to find some way to atone), Buddy Eagleton, myself.

King, Stephen

The Mist