Scott Reilly

This plugin allows you to easily define help text that appears when a visitor hovers their mouse over a word or phrase in a post or page.
Via the plugin’s settings, simply specify the words or phrases that you want to be associated with hover text, and of course, the desired hover texts themselves. The format is quite simple; an example of which is shown here:
<pre><code>WP => WordPress
Matt => Matt Mullenweg
The Scooby Shack => the bar where the gang hangs out
</code></pre>
Additional features of the plugin controlled both via settings and filters:
<ul>
<li>Hover text can be enabled for comments (it isn’t by default)</li>
<li>Hover text can be made case insensitive (it is case sensitive by default)</li>
<li>Hover text can be limited to doing only one replacement per term, per post (by default, all occurrences of a term are given hovertext)</li>
<li>Hover text can be rendered using the default browser tooltip (by default, the better-looking <a href="http://qtip2.com/" rel="nofollow ugc">qTip2</a> library is used)</li>
<li>Hover text can be expanded to affect other filters</li>
</ul>
Note: This is not the same as my <a href="https://wordpress.org/plugins/text-replace" rel="ugc">Text Replace</a> plugin, which defines terms or phrases that you want replaced by replacement text when displayed on your site. Text Hover instead adds the hover text as additional information for when visitors hover over the term, which is otherwise displayed in the post as you typed it.
Links: <a href="https://coffee2code.com/wp-plugins/text-hover/" rel="nofollow ugc">Plugin Homepage</a> | <a href="https://wordpress.org/plugins/text-hover/" rel="ugc">Plugin Directory Page</a> | <a href="https://github.com/coffee2code/text-hover/" rel="nofollow ugc">GitHub</a> | <a href="https://coffee2code.com" rel="nofollow ugc">Author Homepage</a>
<h3>Developer Documentation</h3>
Developer documentation can be found in <a href="https://github.com/coffee2code/text-hover/blob/master/DEVELOPER-DOCS.md" rel="nofollow ugc">DEVELOPER-DOCS.md</a>. That documentation covers the numerous hooks provided by the plugin. Those hooks are listed below to provide an overview of what’s available.
<ul>
<li><code>c2c_text_hover_filters</code> : Customize what hooks get text hover applied to them.</li>
<li><code>c2c_text_hover_third_party_filters</code> : Customize what third-party hooks get text hover applied to them.</li>
<li><code>c2c_text_hover_filter_priority</code> : Override the default priority for the <code>c2c_text_hover</code> filter.</li>
<li><code>c2c_text_hover</code> Customize or override the setting defining all of the text hover terms and their hover texts.</li>
<li><code>c2c_text_hover_comments</code> : Customize or override the setting indicating if text hover should be enabled in comments.</li>
<li><code>c2c_text_hover_case_sensitive</code> : Customize or override the setting indicating if text hover should be case sensitive.</li>
<li><code>c2c_text_hover_once</code> : Customize or override the setting indicating if text hovering should be limited to once per term per piece of text being processed regardless of how many times the term appears.</li>
<li><code>c2c_text_hover_use_pretty_tooltips</code> : Customize or override the setting indicating if prettier tooltips should be used.</li>
</ul>

Text Hover

Add hover text (aka tooltips) to content in posts. Handy for providing explanations of names, terms, phrases, abbreviations, and acronyms.

Nazmi Aydogdu

Lightweight content optimizer, use for a better #a11y !
Automatically add hints/explanations for abbreviations or acronyms to all of your content.
You can use this plugin if you want to improve the accessibility of your content, especially if you often use acronyms or abbreviations.
Note : 
* For a given word, tag will only be added at first occurrence.
Coming soon : 
* lang attribute support

ABBR Hint Content

Automatically add hints/explanations for abbreviations or acronyms to all of your content.

Text Hover vs ABBR Hint Content