One of the biggest pet hates of serious fans of LEGO is people referring to the bricks or sets as ‘Legos’. LEGO is a Danish word that comes from the two words “Le” (Play) and “Godt” (Well). The correct pronunciation is not ‘Lay-go’, it’s pronounced with an ‘e’ sound like ‘Leggo’. Formally LEGO is written in block capitals, but it can also be written as Lego; all lowercase ‘lego’ is completely incorrect.
When used as a noun, LEGO should only be used to refer to the company. In other cases it should be used as an adjective, like when referring to ‘LEGO bricks’ or ‘LEGO models’. It’s when people try to use LEGO as both a singular and plural known that they become confused and add the ‘s’ on to the end.