while the OED doesn't have entries for rilea, it has rile, and riley, which seem to refer to a thick and turbid, or muddy liquid. I would imagine this might be just a way to refer to wort, or the mash somehow, these being thick and muddy looking liquids. here are the entries
rile, n.
A thick or muddy condition of water or other liquid.
1848 LOWELL Biglow P. Ser. I. Poems 1890 II. 124 'T 'll take more fish-skin than folks think to take the rile clean out on 't. 1859 BEECHER Life Thoughts Ser. II. 7 The muddy bottom sends its rile through all the waters.
riley, a.
1. Thick, turbid, muddy.
1825 J. NEAL Bro. Jonathan I. 369 A gallon o' ryley water..right out o' the spring. 1828 CUNNINGHAM N.S. Wales II. 55 An American landlord brought in a jug of water, and apologised for its being so riley. 1850 PANGBORN Diary in Amer. Hist. Rev. (1903) IX. 105 Got more black rily Coffee and eat sea Bread. 1861 CATLIN Life among Indians 16 The mud and water in the ‘Lick’ still riley with their recent steps.
another possibility is that it may have something to do with 'rill', as a verb, which means
1. intr. To flow in a small stream.
1610 [see the ppl. a.]. 1651 BIGGS New Disp. 144 The profuse sweat, that rills through..the pores. c1709 PRIOR 2nd Hymn Callim. 153 The wholesome Draught from Aganippe's Spring..gently rilling Adown the Mountains. 1821 CLARE Vill. Minstr. I. 106 May showers never fail.., Nor suns dry the fountain that rills by its side. 1855 BAILEY Mystic 44 Time's sand-dry streamlet through its glassy strait Rilled restless. 1884 SALA in Illustr. Lond. News 30 Aug. 195 A small fountain rills from the rockwork.
2. trans. a. To form by flowing. b. To utter in liquid notes.
1845 HOOD Stag-eyed Lady xiv, Then closed the wave, and then the surface rill'd A ring above her, like a water~knell. 188. SCOLLARD Summer Song ii. (Funk), The brook is dry; its silver throat Rills song no more.
3. To make drills in (a garden bed). rare1.
1658 EVELYN Fr. Gard. (1675) 244 For this you may make use of the houe, rilling the bed where you would set them.
Hence rilling ppl. a.
1610 W. FOLKINGHAM Art of Survey I. ii. 40 The grauelly colde of rilling fountaines. 1797 F. BAILY Tour (1856) 260 Vortices, which..cause a rilling, murmuring sound. 1853 F. W. NEWMAN Odes of Horace 207 What boy these cups of hot Falernian Tempers quick with rilling water?
3 especially puts me in mind of the lautering process. that may be a long shot.