The fiftieth is assigned eloquence and communication. Following how that assignment relates to the rest of its position is a useful exercise, because it shows the machinery.
The fiftieth angel holds five degrees of Aquarius, within a decan with a planetary ruler in the Chaldean order, corresponding to a minor arcanum in the Golden Dawn tarot attribution, within the octad assigned to a sephirah and its archangel and choir. That is five independent coordinate systems, all fixed once the position is fixed.
The office is the only element with no derivation at all. It is not entailed by the sign, the decan, the planet, the card, the sephirah or the name. It was assigned, and the assignment reaches modern lists through the nineteenth-century French tabulations.
Once assigned, however, it tends to be rationalised against the other coordinates, an office of communication read as fitting an airy sign, or a sephirah of foundation, or a particular card. Those readings are constructed after the fact and are not difficult to construct, because with five coordinate systems available something will always fit.
That is the general shape of correspondence systems, and it is not a criticism peculiar to this one. The Golden Dawn's tables work the same way, as do most of the tabulations in the wider literature: a large grid, many columns, and a strong presumption that any two entries in the same row must be related.
The presumption is what makes such systems generative and interesting to work with. It is also what makes them unfalsifiable, and a reader should be clear which of those two properties is doing the work when a correspondence seems particularly apt.