TBF, it's been called Tieto-something for thirty years or so. The most recent merger is visible as a suffix until the next one. Except if there isn't one for a while, then they revert to just Tieto after a few years.
Source: Worked at "TT Tietotehdas" (organic part of the name, not a suffix, AIUI) in 1996 and have had to do with it every now and then after that.
On the “suffix” side there was EDB -> rebranded EDB -> EDBErgoGroup -> Evry in several years. Also changed hands following a loss of major customer in 2015 before being merged with Tieto
Source: Worked at "TT Tietotehdas" (organic part of the name, not a suffix, AIUI) in 1996 and have had to do with it every now and then after that.