Fferm ym mhlwyf Llanddeiniolen, Sir Gaernarfon yw Cefn Llan - cartref y teulu Hughes. Annibynnwyr oeddynt a daeth dau o'r meibion yn bregethwyr. Mynychodd Griffith Hughes Goleg Hackney a bu farw ym 1837 a daeth David Hughes (1813-1872) yn bregethwr yn Nhredegar. Cychwynodd ef bregethu pan yn 19 oed yng Nghapel Bethel ac aeth o Academi Hackney i Glasgow, lle cafodd ei radd. Cafodd ei ordeinio yn St. George's a Moelfre, Sir Ddinbych. Symudod yna i Lanelwy, wedyn Manceinion, ac yna Bangor cyn cyrraedd Capel Saron, Tredegar ym 1855. Arhosodd yno hyd ei farw ym 1872. Roedd yn awdur ac yn gyfrannwr cyson i'r Gwyddoniadur.
Cefn Llan was a farm in the parish of Llanddeiniolen, Caernarfonshire, home to the Hughes family. They were a family of Independents and two of the sons became preachers, Griffith Hughes, who went to Hackney College and died in 1837, and David Hughes (1813-1872), who became known as the Rev. David Hughes of Tredegar. He began preaching at 19 at Bethel Chapel, and proceeded from Hackney Academy to Glasgow, where he is said to have gained a degree, although his name does not appear in the University's 'Roll of Graduates'. In 1841 he was ordained pastor at St. George's and Moelfre, Denbighshire, and was there until 1845. For a period ending in 1846 he was also pastor at St. Asaph. He took over the church at Great Jackson Street, Manchester, from July 1846 until May 1847, when he removed to Bangor to keep school, preaching occasionally on Sundays. He resumed pastoral care in November 1855, at Saron, Tredegar, Monmouthshire, where he died in 1872. He was also a writer, and many of the articles in Y Gwyddionadur are by him. In 1852 he published in Bangor, "Geiriadur Ysgrythurol a Duwinyddol" . He also published "Elfennau Daearyddiaeth" (1859) and brought out a 2nd edition (with additions) of the "Welsh Dictionary" by 'Caerfallwch' (Thomas Edwards).