spud (n.) Look up spud at Dictionary.com
mid-15c., "small or poor knife," of uncertain origin probably related to Danish spyd, Old Norse spjot "spear," German Spiess "spear, lance"). Meaning "spade" is from 1660s; sense of "short or stumpy person or thing" is from 1680s; that of "potato" is first recorded 1845 in New Zealand English.