The General Conference on Weights and measures both defines and names units. This body which was set up to govern the metre and kilogram in 1875 eventually grew to define the SI system in 1960. The ninth conference in 1948 was the first one to name units after deceased scientists. Names are chosen to honour the achievements of the scientists involved. Here's a nice metrology site going into more detail.

https://www.bipm.org/en/worldwide-metrology/cgpm/

Edited to add : Completely forgot that the Amp Volt and Ohm predate 1948 these units were first defined by the British Association in 1873