Early 18th century; earliest use found in Medleys. Perhaps (i) irregularly from classical Latin altum the deep, the sea, use as noun of neuter of altus high, deep + -al;.
Definition of altumal in US English:
altumal
adjective
slang, rare, archaic
Of or relating to sailors or the sea; nautical.
Origin
Early 18th century; earliest use found in Medleys. Perhaps (i) irregularly from classical Latin altum the deep, the sea, use as noun of neuter of altus high, deep + -al;.