What does "P.S." mean on Aeropostale clothing for kids?

The Aeropostale clothing brand "P.S." is an abbreviation for Pint Sized, explains The Motley Fool. This line of clothing is Aeropostale’s children’s line created for children age 4 through 12, and is available online and in multiple states.

Aeropostale is a teen apparel store that designs, sources, markets and sells its own clothes. The first store opened in 1987 in West Los Angeles. As of 2014, the company has over 900 stores operating in the United States. French for Air Mail, Aeropostale debuted its P.S. children’s line in 2009 targeting 7 to 12 year old children, and two years later added clothing for children as young as 4.