Acaill is based on the Watts font used in the early 19th century.

The Macintosh versions of these fonts are encoded according to the Mac Gaelic Roman character set, which has been the standard character set for Gaelic fonts on the Mac since 1993, when the Irish localization of Mac System 6.0.8 and 7.1 were released. The PC versions of these fonts are encoded according to ISO/IEC 8859-14 (Celtic), with some standard Windows extensions between x80-x9F. These fonts, unlike many Celtic fonts, are suitable for writing, and for text interchange between, the Irish and Welsh languages (Breton, Cornish, Manx, and Scottish Gaelic are served by ordinary Mac and PC character sets).