Green’s Dictionary of Slang

tearful, prone to crying; thus watery head n., one who cries.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 191: A watery head hath the wife, whose nob, like Niobe’s, is all tears.
1830		Egan Finish to the Adventures of Tom and Jerry (1889) 149: She was apprehensive that watery-headed jack would never get over his troubles without ‘piping his eyes.’.
1846		Swell’s Night Guide 135/2: Water-headed, a snivelling fellow.
1862		E. de la Bédollière Londres et les Anglais 318/2: watery headed, individu à tête humide, qui pleure aisément.
1866		J. Greenwood Little Ragamuffin 115: We don’t want no snivellin’ in our wan neither, so I can tell yer, jolly young watery head!
1899		Boy’s Own Paper 13 May 518: Gahn, old watery head! Piped his eye ’cause he warn’t going.