A gnauga mask, in traditional Venetian iconography, is a half-mask depicting a domestic feline: that is, a house or alley cat.
The persona is that of a down-on-her-luck widow who has several mouths to feed other than her own, often suspiciously young. As in, her husband has been dead for how long? Since soliciting for sex in the street was questionable, and mostly illegal, and begging for alms had at least a varnish of respectability, this was often a way to circumvent arrest if not suspicion. To add verisimilitude, she was accompanied by some urchins, and/or a baby (either real or a doll) in a Moses basket with a handle. Since Mrs. Cat was, well, a cat, the baby was replaced with one or several toy (or real) kittens, while affecting an otherwise human female (but very bosomy) ragged/vampish costume. A gnaga, similarly, spoke in a high-pitched miaowing tone, alternately begging and cursing, often expressing what she really thought about religion, politics, and sex. (Gnau means Meow in Italian.)
And there the matter might have rested, except that, somehow, young men got into the act. Y'see, if soliciting for sex woman-on-man was illegal, man-on-man soliciting could get you really beat up, beheaded, or banished (not that it made much difference). Since it was fairly clear that a man-wearing-a -woman-dressed-like-a-cat-costume was an actor/entertainer, not really a cat, prostitute, or indeed, a woman begging, it became OK (during Carnival, and other festivals) for men to don the ears and whiskers, improvise boobs, and take up a basket of squirming tabbies, looking for alms, toms or whatever.. Of course, it might just be a woman...Current websites, selling the Masks of Venice, simply talk about how pretty and feminine they are, and suggest they might be worn with an evening gown...
My Gnaga is strictly for charity, and so, we're downplaying the sex, in favor of the comedy. She wears sandals, paw mittens, and a tail, and carries a basket of vintage cat dolls (plush, knitted and cloth) The overall theme is "Spay, neuter, and adopt", with also Toxoplasmosis information. Which is what you might say, if you were a young widow, with a basket full of inconvenient children....