“Urk” is not a standard spelling

Yes, it’s in the Urban Dictionary, but then, what isn’t?

I’ve begun noticing the spelling “urk” where standard English calls for irk.

Headline on the Keene-Valley (NY) Forum: what urks me most

Blog title: Stuff That Urks Me

Twitter Tweet: One thing that URKS ME THE MOST is people who cross the street when it clearly says DONT WALK!

irk: to irritate or disgust (as a person) usually by reason of tiresome or wearying qualities -Merriam-Webster

The etymology of irk is uncertain. It may be related to O.N. yrkju “work.” The modern use of the verb irk with the meaning “annoy” dates from the late 15th century. The adjective irksome, “bothersome,” dates from the 1510s. (Online Etymology Dictionary)

English orthography makes use of five different letter combinations to spell the /er/ sound:
er
her, after, determine
ir
sir, stir, girdle, bird
ur
urn, turn, burn, spurn, pursue, murder, burr, cur
(w)or
work, word, world, worm, worship
ear
early, earth, earl, earn, learn, heard, pearl, search, yearn

Yes, it does seem excessively irksome to have five ways to spell one sound, but that’s the way it is.

The best way to deal with it is to pay attention to words that contain the /er/ sound the first time you have occasion to write them. Romalda Spalding’s mnemonic is an effective way to remember the five spellings:

Her first nurse works early.

In this sentence the spellings occur in the order of their frequency. Most of the time the /er/ sound is spelled er. The “er” of early, on the other hand, represents the /er/ sound in only a few English words.