The pip of a fruit, as in orange or apple pip, is an abbreviation of the 14th century word pippin. According to the OED, the abbreviation is first cited from 1598. Pip meaning a spot or mark on playing cards, dice or dominoes also dates from the late 16th century. Pip as in a star on an army officer’s uniform dates from 1919. Pip as in the electronic time pip that indicates the correct time dates from 1938. See also Give someone the pip.