What is Jno short for?

The Soc.genealogy.britain FAQ: "Abbreviations for Jno and others are:
Alex/Alexr - Alexander
Bernd - Bernard
Chas - Charles
Dy/Do - Dorothy
Edw - Edward
Eliz - Elizabeth (not to be confused with Eliza)
Em - Emma/Emily
Fredk - Frederick
Geo - George
Hon - Honour
Hum/Humy - Humphrey
Jas - James
Jno - John
Jonth - Jonathon
Jos - Joseph
Josh - Joshua/Joseph
Marg - Margaret (not Mary)
Mart - Martha (not Margaret)
Mattw - Matthew
My - Mary
Ric/Richd - Richard
Robt - Robert
Saml - Samuel
Ste - Stephen
Tam - Tamsin/Thomasin
Tho/Thos - Thomas
Wm - William
Xian - Christian
Xpr - Christopher

There is an excellent tutorial by Sabrina J Murray on deciphering old handwriting online, which also provides other examples of Christian name abbreviations, plus information on the 'leading s', occupations, numbers and letters. It's no longer available at the given URL

Old handwriting :: deciphering old handwriting in genealogy

Old Handwriting: "In a search through the census schedules, it is helpful to become familiar with a few variants of spelling and letter formation. Until the turn of the century (1900), spelling was phonetic, words were spelled as they sounded. To obtain complete use of any index, it is important to anticipate the different possibilities then to use the index accordingly. Each scribe had his own peculiar style. Nevertheless, it is possible to form some generalities, the study of which will greatly improve the thoroughness of research."