It's not easy to construe the meaning of a word from a single use. Here's the first part of Jonah's poem:
[BIBLE]
Then Jonah prayed to the Lord his God from the belly of the fish, saying,
“I called to the Lord out of my distress,
and he answered me;
out of the belly of Sheol I cried,
and you heard my voice.
You cast me into the deep,
into the heart of the seas,
and the flood surrounded me;
all your waves and your billows
passed over me.
Then I said, ‘I am driven away
from your sight;
how shall I look again
upon your holy temple?’
The waters closed in over me;
the deep surrounded me;
weeds were wrapped around my head
at the roots of the mountains.
I went down to the land
whose bars closed upon me forever;
yet you brought up my life from the Pit,
O Lord my God.[/BIBLE]
From this alone, you might mistakenly conclude that Sheol is the name of the fish that swallowed Jonah.
If you take all the Bible references into account, you can see that Sheol is referring to the place of the dead. Note that Jonah's poem is highly figurative - he did not literally go to the roots of the mountains or to the land whose bars closed on him forever.
If you have an alternative understanding of the word
@Alley Oop, it would be good to know what it is.