We were talking yesterday about whistling and types of whistles.  First let's talk about some of the different types of whistles.

There’s the whistle to get somebody’s attention –

The whistle for a cab –

Casual whistle while you walk down the street –

And the catcall –

Where’d the catcall come from? Most references say it started with the Navy General Call using a boatswain’s pipe –

After spending weeks at sea, when a navy ship would return to its home port or arrive at any port the guys were on the lookout for good looking girls. When one came near the ship one of the guys who had the whistle would blow on it to alert the other guys to take a look. Civilians didn’t know what it meant. Neither did the girls, except if they’d look up at the deck of the ship there’d be dozens of guys looking down at her.

Eventually, when the guys would see a pretty girl on the streets they’d just put their fingers in their mouth and whistle. Over the years the tones of the General Call emerged into what we call the catcall today.

SOURCE: wikipedia