The correct spelling of the word for a sommelier specializing in wines from the Rhine region is "Hummelier." The word is pronounced /hjuːməljeɪ/ with stress on the second syllable. The "h" in "Hummelier" is silent, and the "m" is followed by a double "m" to indicate that it is pronounced with emphasis. The "-ier" ending is common in French loanwords and refers to a specialist or practitioner of a particular art or craft.