Short answers, pulled from the story.
Scholars classify the Celtiberian language as one of the Hispano-Celtic languages spoken in pre-Roman and early Roman Iberia. The term Celtiberi appears in various ancient accounts without complete agreement among modern scholars.
Celtic presence in Iberia likely dates to as early as the 6th century BC when castros evinced new permanence with stone walls and protective ditches. Aristocratic tombs from the 6th to 5th centuries BC give way to warrior tombs showing weapons disappearing from grave goods from the 3rd century BC onward.
The dominant tribe were the Arevaci who dominated neighbors from powerful strongholds at Okilis Medinaceli. Other Celtiberians included Belli and Titti in Jalón valley and Lusones to east.
Quintus Fulvius Nobilior sent against Celtiberians in 153 BC with nearly 30,000 men arrived late and ambushed soon after with 6,000 Romans slain. Nobilior lost over 10,000 men in campaign including suffering frostbite and death from winter cold.
A March 2019 genetic study published in Science examined three Celtiberians buried at La Hoya Alava between 400 BC and 195 BC. They had high levels north-central European ancestry compared non-Celtic populations Iberia.