Coriander reaches Middle English coriandre through Anglo-French from Latin coriandrum. The Greek history supplies koriandron as one form.
The source gives koriannon as an alternative Greek form, not another step. The unspecified Anglo-French spelling is compressed.
Sources
- Merriam-Webster: coriander
Word History gives the selected forms, the Anglo-French intermediary and the alternative Greek form.
- University of Michigan historical dictionaries · MED9735
Meanings of the older forms on the word path.
- logeion.uchicago.edu · κορίαννον
Meanings of the older forms on the word path.
- Online Etymology Dictionary · coriander
Meanings of the older forms on the word path.
- logeion.uchicago.edu · coriandrum
Meanings of the older forms on the word path.