This is a very puzzling surname, for which there may be several explanations. It appears to be occupational, and to describe a trade, but no such trade description is recorded in the medieval occupations lists. On the other hand the suffix 'er' is also used (mainly in the south of England) to describe a person who comes from or works at a topographical place. As an example, the popular surname 'Brooker' of mainly Sussex origins, describes one who lived or worked by a brook. There is however in Northumberland a village called 'Harle', although originally recorded in 1177 as 'Herle', and translating as 'the heathen temple', and this is a possible origin. Another candidate is as a variant of 'Harlow', the Essex town, recorded as early as the year 1043 as 'Herlawe'. Our opinion is that 'Harler' is or was residential, it may descend from the two places mentioned, or possibly from a now 'lost' medieval village, perhaps associated with the first recording as shown below. What is certain is that the surname of 'Harler' is well recorded in the London area in particular. Examples of early recordings include Thomas Harler who married Dorothie Morrall by civil licence in London, on April 27th 1655, during the 'reign' of Oliver Cromwell, whilst on January 1st 1815, Mary Ann Harler, the daughter of James Harler, was christened at St Sepulchre church, London. The first recorded spelling of the family name is shown to be that of Clemens de Herleghe, which was dated 1273, in the Hundred Rolls of Worcester, during the reign of King Edward 1st, known as 'The hammer of the Scots', 1272 - 1307. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.