The homophone with lark (the bird) likely reinforced the idiom but was probably not the origin of it. “For a lark” is correct as well, OED does not cite “as a l

The homophone with lark (the bird) likely reinforced the idiom but was probably not the origin of it. “For a lark” is correct as well, OED does not cite “as a lark.” The phrase “as a lark” probably emerges as a mixture of “as a joke” and “on a lark.”