thistle (n.) Look up thistle at Dictionary.com
prickly herbaceous plant, Old English þistel, from Proto-Germanic *thistilaz (source also of Old Saxon thistil, Old High German distil, German Distel, Old Norse þistell, Danish tidsel), of uncertain origin; perhaps from an extended form of PIE root *steig- "to prick, stick, pierce." Emblematic of Scotland since 15c.