Prat/prat about

In current British usage, prat is a slightly more intense form of twit, a foolish, ineffectual person and dates from the 1980s. Prat about which means to behave in an irresponsible, ineffectual manner derives from the same meaning and also dates from the 1980s. Those who use the word in this senses are probably unaware that prat is in fact an old word for arse or ass dating from The Middle Ages and which later came to mean vagina. These older usages, however, are now generally obsolete.