What is the abbreviation of the word prompt?

There is no abbreviation for the Word prompt, because the Word prompt only has one syllable. For a Word to have an abbreviation, it needs to have more than one syllable. However, the abbreviation Prompt. may be short for Promptorium Parvulorum, ed. Way, Camden Soc., 1865 (Latin: "Storehouse for children"), which is an English-Latin bilingual dictionary completed about year AD 1440.