the.com/willy

means A chiefly British, mildly childish term for the penis, often used with kids or for comic understatement.

from A pet form of the name William — the same affectionate habit that turns Robert into Bob or Richard into Dick gave William a cheeky second life as slang. Nicknames for men's names have long drifted into slang for male anatomy (compare 'dick' from Richard, 'johnson' from John), and 'willy' slid down that same well-worn path, settling into British usage as the softer, nursery-safe alternative to blunter words.