the word 'squiggly' is a modern english formation, first appearing in the late 19th century. it is built upon the verb 'squiggle', which is an expressive, likely imitative word suggesting a quick, twisting, or wriggling motion, perhaps influenced by 'wiggle' and 'squirm'. the addition of the adjectival suffix '-ly' transforms this sense of motion into a descriptive term for lines or shapes that are irregularly wavy or shaky. thus, the word's logic moves from an imitation of a quick, twisting action to a visual description of patterns or handwriting that appear as if drawn with such a motion.

Structure: squigg (to squirm, twist) + ly (adjective-forming suffix) squigg is an english onomatopoeic or expressive formation, imitative of quick, twisting, or wriggling motion. the suffix -ly is from old english -lic, meaning "having the qualities of".