Others will assist with the Greek - but in Latin it's LAH-lah-gay, more or less. Since the stress system in Latin is very unlike ours, it's hard to be categorical, but all syllables are distinct and the first (in this case) is if anything the dominant one. Horace wrote a poem about a girl called Lalage whom he described as 'dulce ridentem" as far as I recall: 'sweetly smiling". Which is nice.
I've heard it pronounced, as a British English name, as if it was Allergy with an initial L. Which is not so nice.