Raspbian Pixel was launched Sept 2016.
I'm not a lawyer nor that familiar with Trademarks, but a quick check on http://www.wipo.int/branddb/en/
# says Google's original trademark for Pixel was registration 5091394 "Date of filing of the application 21.02.2013, Date of the registration 29.11.2016", classifications
"09 Computers; laptop computers; tablet computers; mobile phones
42 Technical support services, namely, troubleshooting in the nature of diagnosing computer hardware".
The first Pixel phone was launched Oct 2016. They hadn't really done anything with the trademark until that point.
Their registration of the "G PIXEL" logo in registration 5186566 was filed 03.10.2016.
They have a pending application registration 87643989 from 12.10.2017 trademarks PIXEL for
09 Computer hardware; computers; tablet computers; smartphones; mobile phones; electronic devices for browsing computers and the Internet, providing access to the Internet, viewing information on global computer networks, voice command and recognition, speech-to-text conversion, personal information management, voice and data transmission, and hands-free use and remote control of electronic devices; multifunctional electronic devices for voice and data transmission; handheld digital electronic devices for recording, organizing, transmitting, manipulating, and reviewing text, data, image, and audio files; wireless communication devices for voice, data and image transmission including voice, text and picture messaging, video and still image camera; wireless communication device for providing real-time translation, for browsing the internet, for transmitting voice and data, for providing and managing personal information, and for providing hands-free use and control of computers, tablets, phones, and PDAs; computer and hardware microprocessor chips; computer and hardware chips for mobile devices, namely, laptops, handheld computers, tablets, wearable headsets, mobile phones, and smartphones; data processing and machine learning systems composed of computer chips, computer hardware, and software; computer operating software; computer application software for use with smartphones, tablets, handheld computers, audio/video equipment, cameras, wearable computers, smartwatches, and wearable computing devices, namely, for allowing the user to interact with, exchange data with, remotely control and make optimal use of the features of all aforesaid mobile computing devices and for the retrieval, download, storage, transmission, and display of digital content, computer software, computer games, audio works, visual works, audiovisual works, electronic publications, books, movies, and music; computer software for voice command and recognition, speech-to-text conversion, personal information management, and accessing, browsing, searching, downloading, and manipulating online databases, audio, video, and multimedia content; audio speakers; earbuds; earphones; headphones; microphones; power adapters, battery chargers, electric charging cables, and cases specifically adapted for and used for charging earbuds, earphones, and headphones; cushions, pads, cases, covers, and protective covers specially adapted for mobile phones, smartphones, and electronic devices; computer peripherals, namely, hands-free devices, headsets, keyboards, chargers, batteries, power adapters, styluses and cables, all for use with computers, tablets, mobile phones, and smartphones
42 Design, development, and testing services for others in the fields of integrated circuits, semiconductors, microprocessors, and computer hardware for signal processing, signal conversion, signal filtering, wireless communication, and audio, visual, and data processing
TBH it was partly just bad timing. As with most companies they don't announce new products in advance, so we weren't to know that they were going to use the adopt the term for their new phones. I thought there was a trademark sweep done before having chosen the name, but i wasn't involved so won't speculate.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
I'm not interested in doing contracts for bespoke functionality - please don't ask.