A word made up by
people uneducated in the ways of etymology. NOT THE PLURAL OF PENIS.
The rule with aplural form with an I is derived from latin and is only applicable when the word ends in -
US, and has no relevance whatsoever when the word ends in -IS.
When a word ends in -IS, the correct plural form is, in
fact, -ISES.
(US-I)
The Octopus was languid.
The Octopi were languid.
The radius was 5cm long.
The radii were both of the same length.
The Hippopotamus was
huge.
All the hippopotami were
huge.
(IS-ISES)
Within most species the penis is used for reproduction.
The correct plural or penis is penises, not penii.
The
White Ibis is my favourite of all the Ibises.