French word lundi comes from Latin dies, Proto-Indo-European *lewk-, and later Proto-Indo-European *lówksneh₂ (Moon.)
| Dictionary entry | Language | Definition |
|---|---|---|
| dies | Latin (lat) | (often in the feminine) A set day: a date, an appointment.. A day, particularly:. A solar or sidereal day of about 24 hours, especially (historical) Roman dates reckoned from one midnight to the next.. Daytime: a period of light between sunrise and sunset. |
| *lewk- | Proto-Indo-European (ine) | |
| *lowksneh₂ | Proto-Indo-European (ine) | |
| *lewksnā | Proto-Indo-European (ine) | |
| *lówksneh₂ | Proto-Indo-European (ine) | Moon. |
| *louksnā | Proto-Italic (itc-pro) | |
| losna | Old Latin (itc-ola) | |
| luna | Latin (lat) | (figuratively) a month. (figuratively) a night. A crescent shape. The Moon. |
| dies Lunae | Latin (lat) | Monday. |
| *Lunae dies | Vulgar Latin (la-vul) | |
| lundi | Old French (fro) | Monday. |
| lundi | French (fr) | Monday. |