Mandé and Maundy are connected, yes:
(C&P-ed from wikipedia)
"Most scholars agree that the English word Maundy in that name for the day is derived through Middle English and Old French mandé, from the Latin mandatum, the first word of the phrase "Mandatum novum do vobis ut diligatis invicem sicut dilexi vos" ("A new commandment I give unto you, That ye love one another; as I have loved you"), the statement by Jesus
in the Gospel of John
(13:34) by which Jesus
explained to the Apostles the significance of his action of washing their feet. The phrase is used as the antiphon sung during the "Mandatum" ceremony of the washing of the feet, which may be held during Mass or at another time as a separate event, during which a priest or bishop (representing Christ
) ceremonially washes the feet of others, typically 12 persons chosen as a cross-section of the community."
But: Daguerre wasn't born on Maundy Thursday. And traditionally-given names tend to be fairly common, but Mandé is very rare/almost unique. So I don't think that's why he had the name. It seems more likely to me that it's a family surname used to commemorate an ancestor - Mandé, de Mande and Le Mandé are all French surnames. Or maybe it's the name of an obscure saint; there are places in Paris