Better question is what 4 letter words I can even remember. Let's see...

fuck, lock, cock, yiff, bear, fair, mare, fare, Mars, SARS, cars, arse, bars, tree, pine, mine, dime, fine, lime, blue, moon, soon, tone, moan, loan, lawn, down, fawn, leek, meme, joke, yolk, dick, lick, sick, tick, kick, ball, mall, fall, chip, ship, spin, meat, meet, porn, corn, horn, burn, role, play, star, trek, mono, long, song, dong, monk, duck, luck, suck, rack, deck, card, nano, pico, mini, cake, sake, lake, aqua, cyan, Arch, lore, vore, fart, dart, mart, sour, hour, four,...

There's probably a website for that, what am I doing. I'll go with Mars Arch.

Interesting how my brain picks the words.

Edit: Removed duplicate word

Edit 2: Remembered a better candidate