Words with a silent protective u after a g when unneeded? I think the u in guest, guess and guerrilla is there to protect the g but how about guard, guarantee, gauge, guitar, guild, guilt, and guide? And again and bargain? Are these 2 sound changes?
Also looking for a list of words that counter the g followed by e, i, y rule.
And why is rugged and tugged pronounced differently?
Also a bit curious as why rugged gets the id sound and mugged, lugged and tugged do not)?
Here are some answers to your good but surprisingly complex questions:
(1) Since <g> spells the soft [j] sound only if followed by <e>, <i>, or <y>, to protect it — or keep it spelling the hard [g] sound — you only a need a <u> before <e>, <i>, or <y>, which, as you point out, explains the <u> in guest, guess, guerrilla, as well as guitar, guild, guilt, guide, and less commonly before <y>, as in guy and plaguy.
The <u>’s in guard and guarantee are there for etymological reasons, though not highly explanatory ones: Each is a doublet of a word with <w>, ward and warranty respectively. Guard and guarantee came from French, and in early French the <gu> was pronounced [gw], later simplifying in some dialects to [g], in others to [w], thus the doublets. (Gauge, gage ’personal pledge’ are doublets of wage.) The <u> came into English spelling of guard and guarantee quite late 15th and 18th century respectively. In modern American English gauge &squo;measure’ is a variant of the less problematic gage, and we still have gage with the sense ’personal pledge.’
Again and bargain behave themselves so far as the <e, i, y> rule is concerned. They just have the unusual <ai> spelling short <e> and short <i>, as in against, Britain, renaissance, said.
(2) Concerning rugged, tugged, mugged, lugged:
In the last three tugged, mugged, lugged the -ed] is the past tense inflectional suffix, which is regularly pronounced [d] after voiced sounds like [g], [b], [j], [l], [m], [n], [r], [and [z], as in your tugged, mugged, lugged, and also in stubbed, judged, stalled, stemmed, stunned, stirred, buzzed, etc. — all of which are one-syllable words. (The inflectional suffix -ed] is pronounced [t] after voiceless sounds like [ch], [f], [k], [p], [s], and [sh], as in lunched, laughed, whacked, stopped, sassed, mashed. It is prounced [id] after [d] and [t]: headed, heated.) But the -ed] in rugged ’rough’ is not the past tense inflection; and earlier spellings suggest that it was from the start a two-syllable word: rogget, roggyd, ruggyd, ruggid. At some point people apparently assumed that it contained the derivational suffix -ed] that marks adjectives (as in hardheaded), but it kept its two-syllable pronunciation.
(3) In the following words in the CommonWords database<g> spells the hard sound [g] in defiance of the <e, i, y> rule: anger, begin , eager , finger , forget , forgive, geese, geisha, gestalt, Gestapo, get, geyser, gift, gild, gill, girdle, girl, give, hamburger, hunger, linger, longer, tiger, together.
By way of explanation of at least some of these holdouts:
The letters <e, i, y> today normally spell high front vowels — that is, vowels that are pronounced high and toward the front of the mouth: short and long <e> and <i>. But some words that today have <e, i, y> spelling come from words that earlier had non-front vowels and thus hard ’s. Some examples are (probably) finger, geese, gild, gill, girdle, girl, together . Some words that today end with <er> come from earlier words that ended <re>, in which the <g> would spell hard [g]: tiger, anger, eager . Some verbs — like begin, forget, forgive, get, give — have past tenses and past participles that contain non-front vowels, which may have caused the modern <g> to be hard through analogy. Finger, hunger, linger, longer, anger are derived from earlier words that ended with [ng] + [g] (as in the middle of single, so the modern <g> remained hard. Some words are recent adoptions from foreign languages that have kept their foreign pronunciations: geisha (fr. Japanese), geyser (fr. Icelandic), and from German: gestalt, Gestapo, hamburger
That is probably more about your questions than you wanted to know and are probably beginning to regret asking.