The name of Gill, according to some authorities, was a nickname for the personal name of Guillaume, the French and Latin form of William. Other historians are of the opinion that it was derived from the residence of its first bearers at a "ghyll" or "gill", that is a deep glen or ravine. It is probable that both theories are correct in various cases. The name is found on ancient British and early American records in the various spellings of Ghyll, Gyle, Gylle, Gyll, Gille, Gil, Gill, and numerous others, of which the form last mentioned is that most generally used in America today.
Among the earliest records of the family in the British Isles are those of Richard filius (son of) Gille of Cambridgeshire about 1273; those of Roger Gille of Oxfordshire about the same time; those of Richard Gylle of Cambridgeshire in 1278; those of Patrick de Gyle or Patrick Gill of Peeblesshire, Scotland, in 1296, from whom descended several generations of John Gills, who held the office of Provost of Perth between 1328 and 1410; those of Robert Gille, Johannes del Gill, and Margota del Gylle of Yorkshire about 1379; and those of numerous others as well.
Of the ancient Cambridgeshire line of the family, Richard Gylle or Gill was living in the later thirteenth and early fourteenth centuries and was the father of a son named Richard, who removed to Hertfordshire and was the father of John, who married Johanna Horne and was the father by her of, amoung others, Richard, William, and Andrew, of whom the first was the father by his wife Elizabeth of John, Leonard, Richard, and others. Of these three mentioned brothers, John married Margaret Canon in 1508 and was the father by her of George, Anthony, Richard, Francis, Michael, and numerous daughters; Richard settled in Huntingdonshire and was the father there of Richard, John, and others, of whom the son John settled in Northamptonshire and was the father by his wife, Sarah Warde, of Phillip, John, and Jane, of whom Phillip was the father of Phillip and Thomas, and John was the father of John, who was the father of Edward, John, and Sarah in the latter seventeenth century.