Forgetful, silly.
Born in 1978, Hilversum, The Netherlands. First used by UK-based employees of Philips Telecommunications (employed at Malmesbury in Wiltshire, UK).
On a business trip to Philips Telecommunications headquarters, some time between January and April 1978, a colleague of mine arrived in his hotel in Hilversum (The Hilvershof), unpacked his suitcase and found he'd left his briefcase at home. Looking around the hotel room, he located a suitable plastic bag and proceeded to use this to carry work-related items to and from work for the duration of his trip.
The bag bore the legend "waszak" - the Dutch word(s) for "laundry bag". Henceforth, anyone doing anything thoughtless was called "waszak" and a new word entered the English language.

When you eat dirt for the first time and leave your family to build a shack in the woods

Born in 1977, Hilversum, NL. UK-based employees of Philips.
Businessman arrived in hotel, unpacked suitcase and found he'd forgotten his briefcase. Looking around the hotel room, he located a suitable plastic bag and proceeded to use this for the duration of his trip.
The bag bore the legend "waszak" - the Dutch word for "laundry bag". Henceforth, anyone doing anything thoughtless was called "waszak" and a new word entered the English language.