This mix-up commonly occurs in the little Sunday school song most of us grew up singing:
"I may never march in the infantry, ride in the ________ , shoot the artillery, I may never zoom o'er the enemy, but I'm in the Lord's army! Yes, sir!"
Most kids grow up singing about riding in the calvary, whatever that might mean! And hey, since this song is sung in church, where the word "Calvary" is used quite a bit in its proper sense, I can't fault the little ones for not questioning its placement in the song. But it makes a lot more sense for them to sing about riding in the cavalry!

Pronunciation: \ˈkal-v(ə-)rē\
Function: noun
Etymology: Calvary, the hill near Jerusalem where Jesus was crucified
1 : an open-air representation of the crucifixion of Jesus
2 : an experience of usually intense mental suffering

Pronunciation: \ˈka-vəl-rē\
Function: noun
Etymology: Italian cavalleria cavalry, chivalry, from cavaliere
1 a: an army component mounted on horseback b: an army component moving in motor vehicles or helicopters and assigned to combat missions that require great mobility
2: Horsemen: "a thousand cavalry in flight"
No real point to sharing this with you...I just wondered if this bugs anyone else, or if I'm the only one that notices when people make this very common mistake!