John Willie and Samuel James are common varieties of the rural Ulster custom of giving children double barrelled Christian names intended for regular use. [former] Rugby international Willie John McBride is better known on the sports pages as Willie John than by his surname.

The same is the case with other bearers of this style of nomenclature, such as Samuel Joseph and William James. Their surnames are rarely used.

A wife asked by a caller seeking her husband 'Is Mr _________ at home?' will often answer, 'Samuel James is down in the meadow', or 'Samuel James is away upstairs to put his head down for a wee minute.'

Ulster kitchen comedies are full of examples of the custom. A double-barrelled name usually labels a member of the cast as a well-off farmer.

In those areas where Hugh is pronounced Cue (as distinct from Belfast, where the general form is Shue) it does not imply that Cue John is an expert snooker player. Women are not immune from the tradition, Mary Jane being the best known form.

The christening custom is common in North America, taken there by Ulster settlers. However, in many cases only the initial of the second name is used, producing such examples as William J., Donald T., and even Harry O.

From the Appletree Press title: John Pepper's Encyclopedia of Ulster Knowledge.
Also from Appletree: John Pepper’s Ulster Phrase Book, John Pepper’s Sez She To Me, John Pepper’s Ulster Haunbook, John Pepper’s Ulster-English Dictionary and Mandeer It's Magic.