For example, instead of spelling it as
extraordinary, you would write it as
This also applies to its derivations, such as instead of
extraordinaire, you would write
I'm aware that in the early days of European metallic typesetting, ligatures were often used as an effort-saving method (less matrices would need to be made). Gutenberg started using his printing press commercially around 1450 CE, and the earliest known usage of the word extraordinary according to the Oxford English Dictionary was in 1460 CE (see below). So it may have been a plausible option for them to have done this for the same reason.
Note: The OED entry requires a subscription, so I included the quote it references here:
c1460 J. Fortescue Governance of Eng. (1714) 39 "The Kyngs yerly expencs stondyn in chargs Ordynarye, and in chargs Extraordynary."