"The history of the term pixel is long and complex 1. A pixel is a portmanteau of the shortening of the words 'picture' and 'element'. Picture element as a phrase is first seen in a publication in 1927, one of the first articles about the new technology of television 2!"
"Pixel does not appear in print until 1965, in a paper presented at SPIE (Society of Photo-Optical Instrumentation Engineers) by an engineer working at the Jet Propulsion Laboratory (JPL) called Fred Crockett Billingsley (1921-2002) 1,2. Its very first use in speech is not known, but it was clearly already being used in engineering circles in 1964 1."
"The term 'pel' (sometimes PEL) as a contraction of 'picture element' has also been used previously as another synonym for pixel but outside specialised fields has never caught on and it is not used in medical imaging."