English
arcanum n.- secret/mystery
Spanish
arcano(a)
Etymology
arcane- understood by few/ mysterious or secret
arcana (n.) 
“hidden things, mysteries,” 1590s, a direct adoption of the Latin plural of arcanum “a secret, a mystery,” from neuter of adjective arcanus “secret, hidden, private, concealed” (see arcane). Occasionally mistaken for a singular and pluralized as arcanas because arcana is far more common than arcanum.
Tom doesn't give a Shit 