From their paper: """ According to the Oxford English Dictionary, a flame or light that is lambent is playing “lightly upon or gliding over a surface without b

From their paper: """ According to the Oxford English Dictionary, a flame or light that is lambent is playing “lightly upon or gliding over a surface without burning it, like a ‘tongue of fire’; shining with a soft clear light and without fierce heat.” And since the light of umbral moonshine is apparently of this nature, we call the six values in Λ = {2, 3, 4, 5, 7, 13} lambent, and we refer to the index ℓ ∈ Λ as the lambency of the connections relating the umbral group G(ℓ) to the umbral forms Z(ℓ) and H(ℓ)g . """ That is some very fine literary influences indeed.