Why was "tantrum" trending last week?
"excrement," a nursery word but a very ancient one (PIE *kakka-), forming the base word for "excrement, to void excrement" in many Indo-European languages; e.g. Greek kakke "human excrement," Latin cacare, Irish caccaim, Serbo-Croatian kakati, Armenian k'akor; Old English cac-hus "latrine."
Etymologists dispute whether the modern Germanic words (e.g. Dutch kakken, Danish kakke, German kacken), are native cognates or student slang borrowed from Latin cacare. The word in this form appears in English slang c.1870, and could have been taken from any or several of the languages that used it (e.g. Spanish, Modern Greek).
[origin uncertain; perhaps fr late 1800s cack, ''to defecate''; perhaps fr dialect cacky, ''excrement,'' attested by 1899; perhaps fr Latin cacare, ''to defecate,'' used as a euphemism in the presence of children; perhaps fr Modern Greek; ultimately fr the Indo-European root kakka or kaka, designating defecation]