Re: cellphone, mobile, handy
Pantaloons comes from a French word Pantalon and refers to typically baggy leg coverings,
Trousers is an English (possible Irish origin) word that refers to a more close fitting garment.
Underpants originally were loose fitting undergamment for the legs somewhere between long johns and boxer shorts.
Over trousers are common in Motorcycling and refer to, often waterproof. trousers that may also ofer some element of protection from surface impact and abrasion.