obj[`${part1}_${part2}`]

let names = ["name1", "name2", "name3"];
let keyz = ["key1", "key2", "key3"];

function contentChart(names, keys) {
  let final_obj = {};
  let obj = { data: "dataSet", options: { text: "placeForName" } };

  for (let i = 0; i < keys.length; i++) {
    const tmpObj = JSON.parse(JSON.stringify(obj));
    tmpObj.options.text = obj${i}-${names[i]};
    final_obj[keys[i]] = tmpObj;
  }
  console.log(final_obj);
}

contentChart(names, keyz);