Henry Mahollam / Mehollem / McHallum servant of the Earl of Moira

I am trying to locate the origins of my 4 x great grandfather Henry Mahollam / Mehollem / McHallum a servant of John Rawdon, 1st Earl of Moira (1720 – 1793) and his descendants the  Marquess of Hastings at Donington Park / Hall in Castle Donington, Leicestershire, England.

Henry was born in Ireland (no place or county given) according to the 1841 census in about 1759 according to his death certificate and burial register entry at Castle Donington, Leicestershire, England. Henry's death notice states that he had served the Rawdon / Hastings family for 72 years as a faithful servant.  So he likely started in service with  the family as a 12 or 13 year old lad.

Henry's occupation in the 1841 census is bricklayer and this is a trade that many of his male descendants also followed.

Henry's wife was called Jane and she was also born in Ireland (no place or county given) according to the 1841 census in about 1763 according to her death certificate and burial register entry at Castle Donington, Leicestershire, England.

I do not know if Henry and Jane married in Ireland or in England.  Baptisms for some of Henry and Jane's children are recorded in the parish registers for Castle Donington.

Henry's surname is recorded with different spellings such as Mahollam / Mehollem / McHallum which makes tracking him down difficult.  The surname eventually morphs fleetingly through Mulholland to Holland which is the surname the direct descendant male lines now use.

Any assistance and information to elucidate Henry's origins will be greatly appreciated.