Multilingual was formed from multi- and lingual. These pieces trace to Latin multus and lingua. The anatomical tongue word also supplies a way of talking about languages.
Sources
- Collins: multilingual
The formation is multi- plus lingual.
- Merriam-Webster: multi-
Multi- comes from multus, much or many.
- Merriam-Webster: lingual
Lingual concerns the tongue and comes from Latin lingua.
- Online Etymology Dictionary: linguist
Also built on *lingua*: linguist, a hybrid from Latin lingua "language, tongue" + -ist