The main variants of the name are IZARD, IZZARD, ISARD. Other variants that have been found are ISEARD, ISNARD, ISSARD, ISZARD but these are very few and think some of these have only come about because of the way the name was spelt by vicars and in census returns. 


It is certain that the name Isard only exist after about 1750, and before that was probably spelt with one Z or two. You must remember that the only people who could read and write around this time were the wealthy and the clergy, so when someone went to baptise a child the Vicar or assistant would ask the names and then enter it in the register and spell it the way he thought was right, hence the differences that occurred, it was quite often, for families to have all their entries in the registers spelt differently every time one was made 


The most common spelling of the name is IZARD or IZZARD and this is still the case to day. If you check out the 1881 British Census you will find  895 IZZARD, 251 IZARD and only 119 ISARD. 


Prior to 1750 those of my ancestors with this name spelt it in many different ways. After this date they seem to have settled on the ISARD version of the name. Although there are a few instances of where the IZARD version has been used.