def _hierarch_keywords(names):
    """
    Prepend the 'HIERARCH ' string to all keywords > 8 characters
    Avoids FITS VerifyWarning.

    Parameters
    ----------
    names : list
        keywords

    Returns
    -------
    new_names : list
        keywords with HIERARCH prepended as apprpriate
    """
    new_names = []
    for cname in names:
        if len(cname) >= 8:
            new_names.append(f"HIERARCH {cname}")
        else:
            new_names.append(cname)

    return new_names