Onion Dasher is not much of a threat, but the player should equip the Safety Bit/Memento Ring to protect against Dischord, as it can have devastating effects offensively especially if the battle drags out.
The adjective of onion refers to the Japanese metaphoric idiom of poverty, aptly named the "Onion Life", "peeling away one layer at a time and crying all the way". Alternatively, the term could come from the slang phrase "to know one's onions", meaning to be very versatile.
Onion Dasher's older translation name Tomb Thumb refers to Tom Thumb, a character of English folklore. The History of Tom Thumb was published in 1621, and was the first fairy tale printed in English. Tom is no bigger than his father's thumb, and his adventures include being swallowed by a cow, tangling with giants, and becoming a favorite of King Arthur.