Note to Twelfth Night, 2.3.27-29, "I did impeticos thy gratillity; for Malvolio's nose is no whipstock: my lady has a white hand, and the Myrmidons are no bottle-ale houses."

Immediately after this speech by the Clown, Sir Andrew says, "this is the best fooling," and so it is, which means that it's only supposed to sound like it might make complete sense. In order to decipher any sense, we have to remember that Sir Andrew says that he sent the Clown a tip of "three sixpence," along with the message, "for thy leman (girlfriend)." The message is merely conventional, like "buy something nice for yourself." Sir Andrew asks if the Clown got the money, and the Clown answers, roughly: "Yes, I put your little gratuity in my pocket (or 'I spent your little gratuity on a petticoat'), because I'm not afraid of Malvolio's long nose which is always into everything, and so I spent it all. It was an expensive night out because my lady has a white hand and therefore expensive tastes, and we went to the ale-house with the the sign of the Myrmidons, and such places aren't those cheap places that sell only ale in bottles."

The Clown, Sir Toby Belch, & Sir Andrew Aguecheek
Stippled engraving by P.W. Tomkins, 1792