Parishioner and congregant refer to members of a particular local faith community. The requirements for membership, of course, vary considerably, but for the most part, simply attending services at a church does not make one a parishioner or congregant of that church any more than visiting a country makes one a citizen of it.
Sectarian considerations govern which is the more appropriate term.
Parishioner is older by a good measure. A parish is an ecclesiastical territory, a section of an episcopal see (e.g. a diocese or archdiocese). Traditionally, any inhabitant of that territory would have been expected to attend services at the local parish church, and all would have been parishioners. The Catholic, Anglican, and Orthodox churches remain organized in this manner, but the term "parish" is used even by some denominational bodies without episcopal administration, so making the members parishioners.
Congregant is broader, in that it refers to the regular members of any local congregation. That local congregation may be a parish, but it might also be a local church or meeting house of a tradition that does not use the term parish, such as the Baptists or Mormons— or for that matter, Muslims or Jews.
To refer more generally to those attending services at a particular time, you could simply say worshippers or attendees; for all adherents, there are a variety of terms employed, such as the brethren or the faithful, or the more mundane churchgoers or the observant; communicants captures the sense of those in communion with the Church as opposed to outsiders.
It's to do with emphasis. "The very house" is a stronger, more particular way of saying "the same". "The very same" emphasises the identity even further. This might seem odd, because the same house is either just the same house or it's not. What is intensified through such usage though, is the interest in, or surprise about, or the odds against the house being the same.
the very same/the self-same (=the same person or thing and not a different one - used to emphasize that what you are saying seems
surprising) [American English] We stood in front of the very same
house in which Shakespeare wrote his plays. - Longmans Dictionary of Contemporary English
Though I don't think it's particularly AmE. While we're considering Shakespeare, we might find:
SILENCE This Sir John, cousin, that comes hither anon about soldiers?
SHALLOW The same Sir John, the very same. I see him break
Scoggin’s head at the court gate, when he was a crack not thus high... -
HENRY IV, Act 3 sc 2
How to explain the use of the modifier? It's in the tradition of the "double superlative", which is well-established usage in English. Just as you can't logically have degrees of "the same", you can't have "most unkindest". But many writers (and speakers) have done/do the very same kind of thing to provide the most boldest emphasis.
- "In profane authors there are also many instances of the use of the double superlative. Sir Thomas More used the expression, 'most
basest'; Ben Jonson that of, 'most ancientest'; John Lilly (of the
time of Queen Elizabeth) that of, 'most brightest'; and Shakespeare,
'most boldest, most unkindest, most heaviest.'" ("On the Language of
Uneducated People," - Quoted in About Education - Double Superlative
Best Answer
'The same' has a determiner and an adjective, so it is leading to a noun. 'As' is not a noun, so the noun must have been elided. The most basic noun is 'thing', so that is what can be implied and inferred. PS: this 'as Y' is also a shortcut, for 'that Y [repeat verb]': 'X means the same [thing] that Y means.'