On a more philosophical stance rather than linguistic terror can be positive. A good thing can be something pleasurable or something that pushes the individual to achieve a more fulfilling state. Terror in art can be pleasurable (see horror films) as stated by Aristotle in his theory of catharsis, see here (where the word terror is used) and here. Basically collectively experiencing fear and pity in a 'safe' environment and as a collective experience 'purges' the soul.
Another aspect of 'terror' that may be judged positive is in the aesthetic experience of the sublime, by which, in a nutshell, the magnitude and strength perceived in nature or in its representation (think: the size of the universe, the number of galaxies, the age of our planet, etc) reminds us of our ephemeral nature.
Several spiritual traditions also attribute many benefits to fear. Fear of God is not considered harmful for example, because it keeps us in the right path. Also in Carlos Castaneda's work, Don Juan, Castaneda's alleged teacher on the path of wisdom, mentions fear (particularly of death) or at least an awareness of it, as a necessary step towards enlightenment.
Therefore it could be the case that when 'terror of God' was a common expression, the meaning of terror had more positive connotations than today.