The blood dripped from his forehead.
Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means drip and the verb vocab version is to drip.
To drip drip drip on your head... what's dripping on your head? You're standing below a toilet that's leaking. The dripping sounds like "sh*tt, ta, ta (したた), with each drip making a "ta" sound because it's kind of thick and poopy.