It’s probably conspiring with the Bart Simpson Chia Pet.
Dear Word Detective: Where did the term “Holy mackerel” come from? — John.
That’s a darn good question, but am I the only one around here who gets creeped out by that phrase? After staring at it a minute or two, all I could think of was the Big Mouth Billy Bass novelty gag I stashed in my closet about ten years ago. I’m afraid it’s mad at me. For the uninitiated, Billy Bass was an animatronic fish, mounted on a plastic wall plaque, that sang such tunes as “Don’t Worry, Be Happy” and “Take Me to the River” while wiggling in a disturbing fashion. Billy Bass was a fad in the early 2000s, and appeared several times on The Sopranos, both as the toy itself and as the inspiration for a talking fish in one of Tony’s dreams. (Said fish was channeling Salvatore Bonpensiero, a mob turncoat Tony murdered and disposed of at sea, and who thus “sleeps with the fishes.”) Anyway, Billy’s somewhere in that closet, biding his time.
“Holy mackerel” is, of course, an interjection expressing astonishment or dismay (“Holy mackerel! What a way to run an army!” 1958), and first became popular around the 1870s. It’s one of a family of such phrases, all appearing in the 19th century, including such hardy perennials as “Holy smoke” (or “smokes”), “Holy cow” and “Holy Moses.”
“Mackerel” are actually a family of several related species of ocean fish that have in common a striped body and deeply forked tail. Mackerel are a popular food fish around the world, but apparently spoil quickly and “stinking like a mackerel” is a common metaphor in literature.
The name “mackerel,” which first appeared in English around 1300, is a bit of a mystery. Probably the most common (and certainly the most entertaining) explanation ties “mackerel” the fish to the Old French word “mackerele,” which means “procurer” or “pimp.” The English form of the French word, also “mackerel,” has been used to mean “pimp” since the 15th century (“Hundreds of ‘night birds’ and their ‘mackerels’ and other vice-pushers were sent packing.”1981).
Tying the name of a small fish to a word meaning “pimp” might seem to pose an insurmountable task, but the human imagination was, apparently, up to the job. The mackerel fish, goes the theory, was called that because people believed that it played an unspecified but important role in the life-cycle of another staple fish, the herring, by somehow facilitating Mommy Herring and Daddy Herring getting together. Personally, I don’t even want to think about how people thought this worked, but there it is. Not surprisingly, most etymological authorities have considered this “fish pimp” theory bunk, not least because no one even suggested it until the 19th century.
As for why mackerel crops up in “Holy mackerel,” the most likely explanation also applies to “Holy Moses.” Both “Holy mackerel” and “Holy Moses” probably arose as euphemistic forms of “Holy Mary,” which might well be considered blasphemous if used as a casual oath or expression of surprise. “Holy mackerel” is apparently just weird enough to pass theological muster.