Quiz: Remember the definition of mal de mer?
late 14c., "accompanying," also "descended from the same stock," from Old French collateral (13c.), from Medieval Latin collateralis "accompanying," literally "side by side," from Latin com- "together" (see com-) + lateralis "of the side," from latus "a side" (see oblate (n.)). Literal sense of "parallel, along the side of" attested in English from mid-15c. Related: Collaterally.
16c., "colleague, associate," from collateral (adj.). Meaning "thing given as security" is from 1832, American English, from phrase collateral security (1720).
collateral col·lat·er·al (kə-lāt'ər-əl)
Indirect, subsidiary, or accessory to the main thing.
Having an ancestor in common but descended from a different line.
A branch of a nerve axon or blood vessel.
A collateral relative.