Been a long time since my Latin days and there's so much nominative/genitive overlap in those words I can't figure it out. "Writings of a fat snake" or something, I don't know. Help? :-)
It's "snake oil font". littera is a letter, and I hope that the plural form means "font" or "script". But litteræ definitely means "science" as well, so that's OK.
Good question. Is oleum used for liquid fat, no matter the source, or is it confined to plant-based oils? pinguis has definite animalistic qualities. You'd think it was oleum nucis indicæ [1], not pinguis nucis indicæ, except when used in a metaphorical manner.