Looking at the popularity of Emma in the database there seems to be a point where it was also used on boys at least based on the numbers, but are all these numbers suspect? The description of the name (see below) seems to suggest it started female and remained so through the 1700s and early 1800s. So is there any actual evidence for it being used as a male name? Like a famous male Emma?
Originally a short form of Germanic names that began with the element ermen meaning "whole" or "universal". It was introduced to England by Emma of Normandy, who was the wife both of king Ethelred II (and by him the mother of Edward the Confessor) and later of king Canute. It was also borne by an 11th-century Austrian saint, who is sometimes called Hemma.
After the Norman conquest this name became common in England. It was revived in the 18th century, perhaps in part due to Matthew Prior's poem 'Henry and Emma' (1709). It was also used by Jane Austen for the central character, the matchmaker Emma Woodhouse, in her novel 'Emma' (1816).