Donnan

Part of speech: noun

Definitions

1. The uneven spreading of charged ions across a semipermeable membrane caused by a charged macromolecule on one side ; a family name, such as that of an early twentieth-century British physical chemist
2. An equilibrium in which mobile ions are unevenly split across a membrane because of fixed charges on one side ; a surname carried by a notable British scientist of the early 1900s
3. The imbalance of ion concentrations that a membrane creates when charged molecules cannot cross it ; a surname shared by a prominent British chemist from the early twentieth century

Etymology: Donnan is a surname, and its story is one of a name shrinking as it crossed into English. It is a reduced Anglicized form of the Irish "Ó Donnáin", meaning "descendant of Donnán". The personal name Donnán is built from "donn", meaning "brown" or "brown-haired", with the diminutive suffix "-án" added to it. So the name began as a nickname for a brown-haired man, and his descendants took it as a family name. The Irish "Ó" prefix, meaning "grandson" or "descendant", was dropped in English usage, leaving only the core name. Over time the surname was simplified to the shorter form seen today, which is how a clan name from Gaelic Ireland came to look like an ordinary English word.