It was not until the early Middle Ages that surnames were first used to distinguish between numbers of people bearing the same personal, or Christian, name.  With the growth of documentation in the later Middle Ages, such names became essential, and a person whose distinguishing name described his trade, his place of residence, his father's name, or some personal characteristic, passed that name on to his children, and the surname became hereditary.

In the case of the German surname Ibach this name is of local or toponymic origin, being derived from the name of the place of residence of the initial bearer.  In this instance, the surname Ibach would appear to be derived from the German Words "iche" meaning an "oak-tree" and "bach" meaning a "stream" thus indicating that the original bearer dwelled near the "oak that was grew beside the stream".

The earliest record of the surname is that of one Hainreich de Ybach who was living in Weingarten in 1244.  Hans Ybacher was a knight in Stuttgart in 1447.  Johannes Ybach was a resident in Marburg in 1537.

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b - born
m - married
d - died