Green’s Dictionary of Slang

dildo n.

[SE dildo, an artificial penis; itself ? Ital. diletto, a (lady’s) delight; thus fig. the lack of autonomous competence of the sexual aid so named; thus Grose (1785): ‘Dildo, an implement resembling the virile member, for which it is said to be substituted, by nuns, boarding school misses, and others obliged to celibacy, or fearful of pregnancy’]

1. a general term of abuse: a fool, an incompetent; also in attrib. use.

[[UK]Ford Fancies Act IV: This gelded hobet a hoy is a corrupted Pander; the page a milke liverd Dildo; my Wife a Whore confest; and I myselfe a Cuckold arrant].
[US]Wentworth & Flexner DAS.
[US]Baker et al. CUSS 105: Dildo A person who always does the wrong thing.
[US]S. King Stand (1990) 185: Those boys are more dildoes than desperados.
[UK]J. Sullivan ‘Go West Young Man’ Only Fools and Horses [TV script] No, he knocked that dildo out in the first round.
[US]C. Hiaasen Native Tongue 118: Get me that dildo Chelsea.
[UK]I. Welsh Filth 151: There’s a pair of comedians in front of me, dressed identically in dark blue suits and ties [...] what a pair of fuckin dildos.
[UK]D. Mitchell Black Swan Green 177: That dildo knew our rules.
[UK]J.J. Connolly Viva La Madness 281: Proper dildo kid, not all there.

2. (Irish) a promiscuous woman.

[Ire]Circuit Court, Dublin; Butler v. Four Star Pizza Mar. n.p.: A pizza courier had been sexually harassing a more senior employee over a seven-month period – grabbed her chest, slapped her bottom [...] called her a slut, a slag and a dildo [BS].

In compounds

dildohead (n.) (also dildobrain) [-head sfx (1)]

(US) a general term of abuse.

Univ. Tenn. [graffito] That’s a left arm, dildo-head! [HDAS].
[US]W.D. Ehrhart Passing Time (1988) 36: What’s that got to do with anything, dildo brain?
[US]S. Morgan Homeboy 233: Here’s a peso, dildohead.