Rattler comes from English rattle plus the agent noun suffix -er, ultimately from Latin -arius, meaning "one who does or makes," descended through Old French -er and Proto-Italic -os.
rattler (English): Anything that rattles; A rattlesnake; A freight...
Definitions
Anything that rattles; A rattlesnake; A freight...
Ancestry of “rattler”, step by step
rattler traces back through two separate lines of ancestry.